People that buy Tower Unite in early access will have probably played or at least heard of gmtower. At risk of making TU simply look like a shiny version of the original gmt I think that some explicitly new features have to be introduced.
The condo layout editor is brilliant for this. Not only does it provide an expression for creativity but it will also be a good way to display just how much potential TU has early in development.
Advanced player customization would be nice but it doesn't inherently add anything to the game other then looking pretty(thats important too!) I would say it should be finished soon if it can be finished but if its severely detracting time from things such as gamemode development than it can wait.
I honestly do not care about workshop support in the early access. The game will probably still be rather buggy and have a small playerbase so I don't think we're gonna get much from it anyway.
I share Caboose's opinion on the casino. It would suck to have the casino all built and prettied up and to not have anything in it. Also the casino minigames already exist in gmt so it might be a bit of a turn off for new players who buy TU coming from gmt and don't see casino games.
Though I'm fairly excited to get an arcade I don't particularly care about when it comes out.
As for what I really wanted? I personally want both the floorplan editor and the casino games equally but I ultimately voted for floorplan editor because of the creative potential and draw it could bring to TU.