This would instantly kill the game.
One thing I read almost as much as ‘there are not enough ascension materials’ is ‘i quit game XYZ because i had to spend hundreds just to keep up’. Whilst I fully agree that a boost in rare quests etc would be good for the game (and supposedly they’re working on additional ways to gain ascension materials), making it possible to directly buy them would make this game straight p2w.
At that point it doesn’t even matter that much anymore that you can gain ascension materials for free as well, because people can buy their way straight to a team of maxed 5*s (might cost a lot, but with the gem prices you’re proposing for materials its pretty cheap).
The fact that everyone is in a similar situation, money or not, with those ascension materials actually makes it necessary to use strategy and creativity. You’re limited in your options so you have to think outside of the box. You can’t ascend both Lianna and Alberich directy off 1 paycheck, who will you use and which other heroes would form a better team with your choice.