There's nothing wrong with tweaking the Stat Bump mechanic when making higher level characters, always put odd values in the stats that are retroactive, or don't have any effect. I always set Int to whatever it's final value should be at 1st level.

Just a thought, have you considered the alternate ranger class? It's identical, except that he trades spells for an extra 10' of movement, plus some extra abilities at higher levels (I'm not sure what, my Ranger's not that high yet.) From your description, it sounds like he could take advantage of the extra movement, instead of spells.

Just a though. Rangers are one of my favourite classes.