I think having the option to use a tank and for it to be a bit more pocketable to be something i would like. Sure it might be on the mod all day, but i think many of us have a lot of parts in our kits that we use on different occasions. It would be useful on a lot of juice supplying mods (Line, Fog, GTank, Genisis LV, UFS, MAP Tanks, etc etc) If it was $20 or so, i think it would sell quickly.
I dunno, as much as it may have limited uses, it is a use i think many woudl liek to have the option for.
An offset MAP tank where the hole is not in the center (providing clearance for it to fit on the Darwin) woudl also be an interesting option. I think someone else was considering making one of those, but havent heard anythign more of it. IMO It seems this angle adapter would be worthwhile regardless.
Has to be someone out there with the skills, and desire to make some cash.