An idea to resolve the gold and iso problems thats fair

Reecespieces101

Option 1
All gold collected from duping a champion is multiplied by 10 which would make the gold gained from a dupe 10000 which is just a little bit
Double the lowest amount of gold in a gold crystal that way people might spend units if they can get more bang for there buck

The calendar
The calendar could fix these as it itself needs a buff every month all players would end with 200000 gold for the calendar and about 50ish teir 5 iso bricks of their chose

For iso

An iso8 crystal
If we had one of these and they were not too rare maybe they could come from summoner advancement anyhow they could give large iso bricks of a certain class these would be the 17k iso bricks we saw in the dual 6 star offer

TheTalents

I've talked about this very issue several times and the amount of gold 6 stars take to rank up. The easiest solutions is to add more iso for 5 star dups and even more iso for 6 star dups.
A quicker fix would be to half the amount of money it takes for rankups but I don't think this is an issue that Kabam wants to be solved due to the "game economy."