Surely the whole point of them buying Liverpool was that the cash was already being generated. They admitted they only went ahead because they thought FFP would prevent others competing, and even then they still wanted to create a "Super" league.
Leeds would have been a good buy for sensible owners in the early 90s, and they can build on their support to move up amongst mid-table clubs, but they're still £300m+ behind Liverpool and that gap can't be breached without significant cash.
I suppose they could take a chance, and use part of the profit to try, but as we've seen with Everton, it can be a huge money pit, and FSG don't look like that kind of outfit.