I don't think we should do that, in my personal opinion.
Reason is that Super Mario Bros 3. is more like NSMB2 than NSMBU is to NSMB2. Then again, I'm not Bun, but I just wanted to give in my two cents
Old 3DS XL info:
I used to have a 3DSafe A9LH V11.3.0-36U with Luma in my CTRNAND. Since ReiNAND Reibooted and Re-Reileased, I "switch"ed back.
Right now, I have boot9strap with Luma 8.0 as my CFW. Though, I'd like to see other CFW's for B9S.