The Nullcraft thing would require mind control, not active help from an opponent, because manufactured truth only works on your own stuff. Still way too much trouble for a win condition.
The T-Rex thing is similarly non viable in real games against an opponent trying to actually win, if only because you'd spend all game not putting down board presence by playing a ton of worker destruction or your opponent is actively assisting. If your opponent is not able to overwhelm you by just playing bodies while you play spells, then I am missing something. If you wanted to use the T-Rex in 2headed mode, you have an even bigger number of workers to destroy before the T-Rex could possibly eat himself.