True, but a "normal" cohort would be constantly gaining xp as well, which could be spent. However I see your point, my point about would let the cohort both spend xp AND level. Perhaps that is too much. Although with a 25 point buy cohort ...
I'm not sure I agree with your numbers, but I will say this: If someone's PC has to stay at the Inn because your torch boy is coming along, that is, in my opinion, unacceptable. Perhaps that is not a popular or commonly held opinion in LEW.
To put a bit of perspective on it, I don't like cohorts, never have. I've seen them allow one player to eat up far too much of the spotlight. Leadership is also usually a no-brainer feat (it's that good). For those reasons I really don't allow it anymore.