If froome is really going to isu, probably he have the guarantee that they will buy some climbers. The most important thing is that froome recovers from is injurys, and returns to is best shape, that s the most difficult thing, but if that happens, no one is at their level, and a couple of climbers, like martin, navarro and maybe nivel, is the enough to win the tour, even if ineos or jumbo have better team.
It's unlikely he can fully recover physically because it's an injury that no one has and that includes people who are much younger having similar injuries. They never got back to their previous levels. This is the exact reason I don't think it makes sense to offer him a contract until he has raced to prove where his level now is. Also as mentioned somewhere ISU is currently at their max for riders. They might be able to move 1 person around this year to bring him in, but it's unlikely they could bring in anyone else this year. Next year sure. Froome hasn't raced since before the Duaphine last year, so he's had a full year off. That's also going to affect racing level.