pukunui
Legend
I'd like to drop the level requirements too. However, I think that would require adjusting the mechanics for the higher level facilities so they aren't overpowered right off the bat.Some of the leveling is based on the old 1E/2E rules where strongholds/wizard towers/thieve's guilds and such didn't kick in until 9th level. Personally, I plan to nix most of the level requirements and drop Bastions to 3rd level myself.
For the most part for what sort of individuals to attract, I'd be inclined to steer towards what you'd likely pick up in Sharn - government officials, entertainers, random adventurers (troubleshooters?) and the like. Sort of like a cross between a lesser Guild Hall and TCircle - get a specialist for a one-off task.
I'm also handwaving the sizes. I'm just going with Cramped = small, Roomy = comfortable size, and Vast = really big. As written, the rules for room sizes are wonky. The rules talk about size in terms of 5-foot squares. However, they also indicate that you can stack them on top of each other, so they probably should have referred to 5-foot cubes. Either way, the maximum dimensions make for some very odd shapes.
Take Cramped with its maximum allowance of 4 5-foot squares. If we assume they actually meant cubes, then you can either have a 10 ft x 10 ft square room with a 5-foot high ceiling, or you can have a 10 ft x 5 ft rectangular room with a 10-foot high ceiling.
The players in my game have a floating tower that is round. I arbitrarily gave it a 50-foot diameter, and they each have their own floor of the tower, with the "ground" floor being a common area. There's a 10-foot diameter circular stairwell in the middle of each floor. I gave them free reign to design the layout of their floors, with Cramped being a relatively small space, Roomy being a bigger space, and Vast being a really big space. It's up to them to determine how their rooms all fit together in the space available.