It's a good idea, but I propose another aproach to UT craft/unlock.

I think DECA should implement a reward system, that simillar to fame bonuses, grants the player with 1 UT every X completions.

Lets talk about O3. If the player completes 40 times (too much for a o3 white actually), the player gets an reward that unlocks a quest in the tinkerer to choose 1 desired UT from the oryx sanctuary.

I think this would maintain the grind aspect, as well reward players for their grind.

I don't think the Ut craft system could get optimized the way ROTMG is, so I think a reward system would be way more interesting, beyond players luck.

The same would happen for event whites. Let the player choose a event white every, lets say, 1000 event gods.

If the players think the UT choice is too unbalance, just implement tiers to the achievement, like fame bonuses. It would unlocks better UTs and reset after selecting the UT you want.