Nice to see someone else using the last quality level as an ultimate quality. But I achieved this by cutting uncommon level and moving everything else up one tier. Besides, I noticed that some things when going up one tier increase their performance by around 1.6 (assembling machines 1-2-3, speed/prod modules, yellow-red ammo). So I used 1.6 as ratio to go from one quality tier to another with skipping a level going from epic to legendary. Besides, I made t2 quality modules have 1.6 times of t1, and t3 is around 1.6 increase from t2. So I'm using quality levels 2,5,10,30. Legendary level was 23 before, that was around 2x of epic, but I really hated 7.9 multiplier, so I cut chances even more (to .005), and started another run. I'm really looking forward to legendary t3 modules. So far I've got 3 epic t3 quality modules.
Well, my initial idea was to be able produce unique items instead of a regular with higher level. But in the end I just played with a few numbers

And the last thing. Spent nuclear fuel recycling becomes self sustaining with t3 productivity modules with quality levels greater than 6 (2 in kovarex, 4 in fuel production, 2 in reprocessing). For example level 10 (legendary in steeper quality) results in 40% t3 productivity modules. That allows to produce 26 fuel cells from 19 u238 and 1 u235, then 26 spent fuel cells into a bit more than 28 u238... Iron and water are basically free in space... Who needs fusion when you can run fission in space indefinitely from a single butch of uranium :D

And even more if you add a mod that remove the 300% productivity limit :) but I like steeper quality because it's even rarer to have good quality items, even more if you reduce the probability ! and the mythic quality can create really strong things at the end and it allows more build with better ups.