Rockwoman, that is a great idea. Djgap's Genisis is made to go with the Indulgence, but then he added a 510 connection that is a brass plate that threads into the bottom of his genisis so you can get to the wiring. Nice feature. Also, he uses SS for the top cap too, not alu. He went with 2 holes in the cap so that you could block one as it is going to be difficult for someone to drill out another hole in SS at home. Also, his threads for the cap go higher, but someone said it impedes getting to the kanthal and mesh, so he will do them lower from now on. I had to pass as I actually don't have a battery mod that it would fit on and it would look awkward.
I would suggest a 3/4" or 7/8" overall OD for all parts, you guys should vote depending on what average sizes your mods are. Since these machinists sound good, and making a smaller genisis is quite difficult, I would even be interested in a 5/8" model, but I'm pretty sure that is just me.
If the top of the tank were not flat but slightly sloped towards the wick, this would help with getting a 'good to the last drop' tank.
Some sort of collar to go around the connection to keep the lines smooth and relieve the stress point would be nice, but probably too trivial.