Seeing how you've added 2 skills slots to the gold hero I have a suggestion.
Allow us to purchase extra skill slots on purple and gold heros for gold examples could be as follows
Purple Heros
Slot 9 100 Gold
Slot 10 200 Gold
Gold Heros
Slot 11 300 Gold
Slot 12 400 Gold
I think a lot of us would be interested in using more skills without removing what we already have and leveled up to higher levels this would allow that.