Yup, you're correct you couldn't prime grenades in X1. We had that functionality on the C4 but not on grenades. I'm not completely sure we'll add it into the game if I'm honest - that's not really how modern grenades work. The timer on the C4 has also been replaced by a remote detonator that I think works better overall, although I'm willing to listen to anyone who wants to make that argument that the old priming mechanics were superior.
The elevation level controller is part of a wider discussion we need to have on how the roof hiding / elevation change camera control works. The old X1 mechanics are one option and I think I probably prefer them overall; giving the player manual control over the camera level and with a button to toggle roof hiding on and off (although some is handled automatically). The current mechanics are more like those used in XCOM where the roof hiding is controlled by whether the building is centered in the middle of the screen or not - if you point the camera at a building, the roof melts away automatically. My technical director is convinced he can make the current system work better and that it'll be superior to the old mechanics, and I suspect I'll give him some time to try that before I make a final decision (potentially also letting the community give feedback).
The predicted TU cost is something that was in X1 too, yeah - we will be bringing it back for X2 before release. For the base management stuff it's very much WIP as to how units are going to be hired in the final game right now, so don't worry about that yet. Yes, you're correct soldiers don't have strength and it is intentional - there's been a long discussion on it in one of the inventory threads I think, but the premise is to stop so much endless loadout fiddling after every mission. Adding Strength back in is a pretty easy task though, and potentially I'll decide to add it back in but make the progression work differently instead.
TBH it's kinda hard to have much of an idea of how much effect removing something has until you can actually play the game and see if you like the new way of doing things, so I'm just going to see how the balance develops and reassess my decisions as development continues.