This is a suggestion.

Can you unlock the limit it has of 20? I hate having to wait to level the skills of the heroes each time I level or each time there is a new hero.
You could either unlock it to everyone or to a certain VIP level. It is just frustrating sometimes.
And this happens at all levels and to non-vip and vip users. In my another account (non-vip) I have the gold and still have to wait, now in my main I just get anxiety when waiting xD If one has the necessary gold, one should be able to use it to level abilities.
Also, if not unlock it, at least increment it to 50 or 100 xD

Yes, i agree with you - limit is a bit small. Of course developers don't inlock limit . Maybe they can rise him for 50. 100 points... I look at this number and it gives me a chills a bit))).

Once Again This suggestion have no merit for them... XD
i think the limit is to ensure some diamond supplies from whales but i doubt that even they pay for it, also This further slows down your hero upgrading progress which means that even if you have all the items to upgrade any given hero to your current Arena level you will still have to wait for upgrading his skills, this SHOULD (i am not sure ofcourse) drastically helps them during new hero releases through box events and Conjuring stones since no one can upgrade a hero in 1 hour and start testing it, this way bad heroes will be reported later on and in this 2-3 day period they will be able to sell it to plenty of people.

Well, if they set an upper limit per VIP level they could get something in return, something like 5 extra per VIP or something like that.
But wanted, naïvely, for everyone to have an upper limit regardless if they are F2P or not.
And they said they were gonna "adjust" some perks of VIP levels, this might be an important one.