What to build next?

[AllYourBass]

I'm starting to gather ideas and design options for my next build and I'm trying to decide what type of bass i want to build next. My original intent was to make a 6 string, but was then given the idea of building a 12 (4x3).
I thought about combining the two ideas to make a 18 string (6x3) but i would have some difficulties to over come, mainly strings and tuning.
In staying with the idea of a 12 strings I've also considered doing a 15 (5x3).

So I'm up in the air as what to proceed with.
I'm open to all comments.

Dave

[Suburban]

How about some invention? Make a 16 (4x4) string. Then you can tune each quartet to a chord and surprise the world.

[Yvarg]

I have been wanting to try what Suburban said for a while now (only I was planning on trying it with a 12 string, the two extra strings for each main note being tuned to fifths and thirds). I vote for either the 18 string or something new. Have fun.

[wilser]

Are you willing to play a whole song with all chords in every progression being Maj7?