I’d be all for that, obviously. The custom potential would be though the roof, not only with artwork, but with cannon ranks and whatnot. It’s too bad something like this didn’t exist, would have made my day a lot easier. 😀
As for rules/guidelines and such, you could include them on a small sheet, detailing etiquette for using custom pieces in games and such, so as to limit the abuse that fan made ships could have on gameplay.
Something else, if custom designs were shared, either online o some other format, you could have a situation whee other people buy the blank slate packs to make a copy of a custom ship they saw somewhere else. I”m not sue what impact that would have on a game that did this, but its something to consider I think.