I would just wait till you actually need to use your dark grid or you pull more copies before deciding, since a LB1 Sammy hammer is still weaker than a MLB raid SSR weapon unless you're hitting exceed cap already (unlikely if LB1 Sammy hammer is one of your better weapons.)
In general though, keeping good weapons apart and bricking separately is still best practice. I would argue that it makes even more sense than before 'cos with the extra floors in tower, most ppl can clear 15F with just a little bit of planning and a basic grid 'cos you can use multiple keys to clear the higher floors that you might have struggled with in the past (slam it with your main element, give up before the boss dies, then finish it on-element.) 15F is already one brick per tower before ranking rewards, which works out to around 6 bricks or 2 FLB a year with a relatively casual approach.
You mean FLB? If you didn't grab all 4 copies from the event to MLB it, I wouldn't brick it. If it's MLB, I would FLB it, since laby weapon FLB isn't that expensive iirc. It has very decent stats for an event weapon with small strength, which is 15% assault 15% defender after FLB (and stinger, but stinger is relatively unremarkable.) It's an excellent placeholder weapon if nothing else, and makes it easier to run lance grid if you pull and brick an Odin lance (Pazuzu will get reprinted, add in Shingen lance and a filler assault SR lance and you have a decent lance grid.)
As for UE, you can just go off-element if need be (unless you're a water main?) I fought every single UE with my light team, even when I was still running Barong as main and using SR weapons - off-element with a good grid can hit harder than an on-element grid that was hastily put together.