I really like how the skill trees include some bonus effects to current spells, ie yetis getting a cleave, but I think it would help diversify each build if we could see some of these synergies being able to be picked before level 15.  By level 15 I often found I was around 12-15 minutes into the game which according to the devs the game would be over most of the time. 

So wouldn't it be nice to be able to either have another type of points to put into picking various improvements to current spells or just expand the trees to include various improvements to all spells, ie at level 5 theres a branch to give yetis increasing cleave and then at level 7 another branch to give yetis a passive chance to stun on hit and give each one of these synergies level ups so one game I can make my demigod have an army of strong tanks or another an army of savage cleaving yetis and my playstyle would be very different but I've only changed my skill pick slightly.

This idea would just give demigod much more replayability because small choices in skills can effect how you play and you can always experiment even more, which is important because there are only a few demigods and having lots of choices in how to play them is important.