I just discovered the existence of 120% eidolons the other day, which apparently will get buffed to 140% at some point. My best eidolons are still the 40% ones from events (even the gacha ones are just 40% unless you get multiple copies of them.) Even with the 30% from soul weapon, the differences between 40% and 140% translate into about 60% difference in damage, which is a lot... If I did my math right, going from 10x slvl20 assault to FLB 10x slvl30 assault only gives you an extra 25%-ish in damage (I know FLB also increases ATK but not nearly enough to get you to an extra 60%; I am also aware that FLB-ing also gives new weapon skills, but they are often not as useful as assault.) Which leads to a few questions:

1. Did I do my math right? 100%+ eidolons are worth more than the assault you get from FLB-ing your whole grid?
2. What content, current or future will that extra advantage be critical? Ones I can think of are:
a. Tower, but I think I can live without 4 turns clear and missing a few floors and just get pink bricks slower.
b. GO - Again, I can live with getting ori slower, but it looks like future GO will get harder, so if I can't get FLB weapons fast enough, will I get locked out of future ori without 100%+ eidolon to compensate?
c. AQ5+, although it sounds like people with a sufficiently strong grid, good hime synergy and PF (I still don't have Shingen) can manage.
c. UE - I am supposedly in the top 250 unions according to last thunder UE ranking. Despite that, we couldn't even clear 400 ult, let alone get 30 mil PP to get the second FLB-able weapon, so any additional firepower will be a great boost there, especially since UE is an important source of free FLB-able weapons. Oh, and it looks like next year's UE will not be reprints, so if I can't MLB it now, it's either pink brick it or stuck at LB2, which is only a slight upgrade to SR LB3 (and no, I don't really want to try to join a top ranked sweatshop union with lots of drama - will be happy with just 30 mil PP and get all the event specific items.)
d. Rag raids. Sometimes my ult raids fail, let alone rag raids, and when guardians or whatever they are called comes...
3. I did not see 140% eidolon for light and dark. Is that intentional? If so, why? Is light and dark considered OP without them for some reason? They don't have union guardians either, though that advantage alone won't make or break the game.
4. Should I reroll for a 120%/140% eidolon? It looks like only the wind one is out on Nutaku, probably thunder coming next. My current account already has 6 light SSR himes, a handful random ones for other elements, my grid isn't great though, can probably grind most of it back in a month or two now that I sort of know what I'm doing. I will not be willing spend more than 1 or 2 mtix per year going forward, so my himes will not be as good as the ones I have now.
5. My other plan is to reroll for 100%+ eidolon and befriend my main account and log into the reroll right before I do GO/tower/whatever tough battles where every advantage counts so that I have reliable access to 100%+ eidolon support. My question is, does that work? As in, the most recently logged in friend will always bubble to the top of your eidolon list assuming you did not use it recently? Will Nutaku or DMM take issue with that?