Your proposal sounds like an astounding amount of development work for minimal reward. They are exploring this idea with Unreals, but look how few Unreals are able to be put out. Maybe not a roulette but one or two of these dungeons retuned and rebalanced for some alternate reward system like Faux Hollows may be a more reasonable ask.

This also completely misses the point of roulettes. SE could make any number of daily missions or special high level dungeons/trials or whatever to provide tomes for veterans. Roulettes aren't for veterans. They bribe us to do them with tomes so we keep the content alive for those who are trying to get their clears.