Yeah, I also see a bit of Masche in him. Except he's taller and better in the air. If he'll be at least half as good as Masche it would already be a good transfer in my eyes but I expect him to be much better, possibly close to Masche level or even better because he's a natural CB. It will be hard to replace Masche when he leaves but I believe Umtiti can do that. If everything works out he'll be our starting LCB for the next 6-8 years after a season or two of adaptation. We can afford that adaptation period because Masche is still playing at high level and Mathieu is a solid backup.
I expect Umtiti to push for Mathieu's role from the start and take it over in second half or until end of the season. If he can take Masche's spot (based on his good performances and not Masche getting worse or injured) in best XI then we'll all know he's the real deal.
OL President Jean-Michel Aulas never sell his players whitout variables. so its 25M + lot of stuffs.
I was using google translate so maybe I missed something but I didn't see any variables mentioned on official statement from Lyon. I guess we'll have to wait until he's signed, maybe Barto or Robert will say more about that during his presentation.
Anyway, I don't really care about variables. If we'll have to pay most of them it will probably mean that Umtiti and/or Barça will be successfull which is all I want.