First of all, allowing the backpack to be expanded is great. I just think that it could be presented in a better way. Instead of marking off all the space that the player
could have, why not keep it from showing at all? So if the player starts off with three rows in the backpack, then only three rows show.
Then as the player progresses and spends points into areas that expand the backpack, it shows up. Each investment opens up more space and may keep the player guessing as to how much space they can max out with.
I know that some players may be upset and think that the new game limits the player, (not knowing) that they can expand it latter. But it will be a whole lot more fun this way.