That's cool.
I guess it depends if this is for custom or replacement solution; sounds like the latter. If I were to replace the tank, which I should, I would want something similar to factory dimensions and maybe a little extra capacity (you do have the option to run low to high, depending if you want to go to track, or a long drive), as well as somewhat looking like the original unit..but, with upgraded materials (stainless would be cool) and better design (lighter brackets, accepting oem equipment, sump design, etc.)...Otherwise, if I were going custom, I would look into the many options out there for aftermarket pumps/filters/senders, etc. and design it for those products.
Mine is dented, but in decent shape; although wouldn't mind having aftermarket tank! There are a lot of fab shops that will take your drawings and make whatever you want, as another custom option...The more you can do, the less it'll cost and the better it will end up.