There were a lot of things the developers wanted to do with the 2008 release, and in Dead Space 2 as well, that they couldn't either due to technical or time constraints. A lot of items have been outlined in various Dead Space retrospectives over the years both written and on youtube. If Motive have all the design documents and assets, and they really are rebuilding things from the ground up then sure the opportunity exists to add stuff, particularly the stuff the original develops wanted in the game. I'm 50/50 on their comments about adding new story beats to the game only so that it makes some things in future games make more sense but...... Ultimately, if they plan on going further with Dead Space remakes and the franchise, imo I feel they'll have to (and should) retcon most of the 3rd game storywise. Those that finished it will probably know why I say that. At the very very very least, the ending.