(which costed a lot of time/gold)
We have no plans to implement something like this. What you said is what is intended - a game needs a gold sink and something to do for max level players. Since the 5th hero gear and weapon is the current end-game gear it shall be hard and not obtainable with a blink of an eye. That includes the desired special options.
There is the same behavior with the PoS set which is even harder because you have to give up your "old" PoS weapon/wings first before having the opportunity to re-farm the materials. For 5th hero you can at least keep the better weapon to farm the materials again.
Plus introducing such item change the overall p2w history of the game which we tried to eleminate as much as possible more into the unwanted p2w direction again.
So the definite answer is: there will be no such item introduced.