Hello, and welcome back to Blockland.
First off, when the first retail screenshots were released many of us, myself included, did not like the new player model. But after playing with it for a while pretty much everyone now enjoys it as much, or better than the original. It can be changed, I suppose, but it wouldn't be that easy.
RTB won't be a "change everything about the game" as it was in previous releases. RTB 2.0 will mostly be a client side mod that includes things such as download managers and other things to do with managing your add-ons, look on returntoblockland.com for more information. AiO mod is dead and will not be coming back.
Fall damage can be turned off through a Pref variable. $Pref::Server::FallDamage or something similar I believe, or you can get the IGSO mod (In game server options), although Badspot said it can be exploited. I think RTB will have options like this when it is released, not sure about that though.
And last, building restrictions. There are ways to get past these, but it's not recommended. The brick rendering system has been completely rewritten, they're rendered in quads instead of tris and non-visible sides are not rendered at all. As such, restrictions have been put in place as to not break the whole game, the "editor wand" of RTB is also now not possible, but don't worry. We all got over it and enjoy the game a lot more now with it's increased realism, I'm sure you will too.