I believe adding level up tomes would be a nice addition to the vendor shop.
I believe this would not be over powered because the stat tomes give 15 main stat and 5 off stats.
A hero level up gives 14 or less on the main stat depending on the hero.
Also there is a hardcap on levels which is 99. Although there is no reason to reach 99 it is nice to have the possibility of reaching it.
A reason this is needed is because usually a few bases gets all the monsters. Leaving the others starved for exp.
Accounting for the skill point I believe 260- 300 lumber would be fair.
