I have to say that reading through the threads, it makes me uncomfortable as a writer, producer, director and actor. At best, filmmaking has lots of iffy situations--locking down locations, cast, costumes, props, etc.--even with a script firmly in hand.
What you're talking about here really pushes the line of the screenwriting forum. However, I think it's important to realize that the script is a production tool and central blueprint for the production. With documentaries you can get away with 'less diligent' cinematography because it's more about editing commentary with b-roll. In narrative, you need more savvy.
As producer or AD, I allow 3 hrs to film one page. If it's a complex scene, I may need to allow 5 hrs. Most time, we can shoot a page in 2 hrs IF there's no equipment problems, location problem, prop/cast problems, sound/lighting issues, etc. Most student projects tend to allow only one hour per page and fall behind. I worked with one student who allowed only 30 minutes per page. Needless to say, many compromises needed to be made come shoot days. WHEN I have a properly formatted script, I can quickly breakdown how much time will be needed for locations and shots. So when you say, "before that, I want to flesh out my scripts, and, quite honestly, I am approaching the time when I want to film, come what may." it causes me to shudder.
As an actor, I have multiple commitments. Of four indie projects, I've received shoot dates for none, though they're all supposed to shoot over the next two months. You can't ask actors to put their careers on hold for an unspecified period of time. Can scripts and locations change? Of course. But once you start shooting, it is a royal pain in the ass if you lose an actor. So if you want to do a table read, be clear that this is not for the film. It may not be what you want to hear, but I'm telling you straight--don't bring in your film actors until you have the final script. If you have acting friends to help with the table read, go for it. BUT your final cast--especially at this time of the year--will have multiple paying opportunities coming at them. Money trumps free/deferred. So a comment like, "like an enhanced table read, so I can get an idea of how the scene would work." also makes me nervous. As an actor, I have worked with a director if the scene didn't feel authentic. Sometimes as a director your take on a character differs from the actor so you provide guidance. Central to both is the underlying story. If neither have a clue 'how the scene would work' it can create a bit of chaos.
Some actors can be prima donnas. When the director doesn't have a firm grip on the story to be told, it can collapse into a battle of wills. What you don't want is to re-cast a role at the last minute or re-shoot scenes. I've seen both happen and it's never pretty. Be clear that the table read is for potential roles but that auditions will be held later. Work out your script issues BEFORE you bring aboard your cast. Bring on your director, DP, Sound Engineer and crew. You need to have a director who can provide the synthesis of the table read and scene work and translate that story to the actual cast. I'm not saying you can't re-use actors from the table read, but have them audition with everyone else.
"Definitely film the table reads. Show the footage to the actors as well so they know what they need to improve upon" Film the FINAL table reads with your FINAL cast, not your planning ones. That will be useless. Since there is no sense of how they should be acting, there's nothing to improve upon at the initial stage. It's just to get ideas. You can film it, but it's only for use by you and the director to make determinations about where to go with the script.
As a screenwriter, I can't imagine how you'd even start a project without the project fully worked out. I'd never go to a producer and say "here's some ideas we can work out." I might pitch a concept to get the go ahead to develop a script but I'd never get the go ahead to shoot an idea that wasn't fully scripted.
If you're going to assemble a crew, you should also bring on board a script consultant/screenwriter. One, they can polish up the existing script. Two, once you flesh out your scenes, they can make the appropriate modifications to the script. Three, a film tells a story, it's not simply a collection of scenes. When you focus too much on scenes, you lose touch with the events that come before and after the scene and the evolving interpersonal dynamics. Actors can bring some of that. But without the guidance of an established script, you can find conflicting backstories arise. If you have a writer/director, all the better because s/he comes at the project with a unified vision.
Since we're in the screenwriting forum, I want to emphasize the importance of script as the movie's blueprint. As AudioAlcove mentioned, as an AD and actor, I love it when things are clean and planned. I know what my commitments are. You need me to shoot this weekend. Fine, I set aside that weekend for your shoot. The location is ours from 1:30 to 9:00, so the crew is in and set up by 2:30. Cast call is 2:00 to allow for makeup and wardrobe checks. We do the blocking on site, run lines so we do our first call at 3:00. We shoot until 6:30, break for a bite, finish any shots by 8:30. We breakdown and move to the next location or wrap and call it a night.
Fundamentally it comes down to respect. If you respect crew and cast, they will give you their all and often for free or very little. Part of that respect is time. Time is a valuable commodity. We all have other things we could be doing. So the concept of "Well, maybe I can get a bunch of actors together to just shoot some scenes to see what might work" reads to me as 'waste of time'. While some producers and directors might think that actors are 'arrogant'--what are you paying them to do multiple reads or act out scenes to give you ideas? I could be auditioning for a paying role, acting on stage, appearing in a paying commercial, working a job, or be involved in any number of things. What makes it worth my while as an actor? Do I get IMDb credit for a table read? If I asked my videography friends to spend a Saturday with me shooting some b-roll just for ideas for a film when they could be getting paid to shoot a wedding or paid movie work, they'd laugh at me.
If you're in film school or have acting buddies with nothing better to do on a weekend, this might be a good exercise. I'd still suggest pizza and refreshments for all involved. The time of talent and crew IS valuable. I'm just suggesting that before you take this approach, you evaluate what your real needs are. Since you feel more confident as a producer than director, you might want to hire someone to polish your idea or bring on a good director and turn over control to them to write/direct as they envision it. I don't say this to diminish your abilities, but as a producer, you make money when you have decisive individuals under you. That doesn't mean that they shouldn't check in with you, but you need someone with a strong creative grip and clear vision.
What I understand from your original post is that your script is still unsettled. You can't get to where Sweetie mentioned until the fairly FINAL script is in place. That meeting IS NOT the place to be writing the script. What Sweetie mentioned is what happens when you have a final script. They had worked out wardrobe and set locations. Yes, there will be minor changes as he mentions. And it is great to have everyone meet. But everyone is fairly clear to the story and only adding enhancements. It's not a time to 'flesh out your scripts'. The meat should already be on the bones at that point. Good luck.
