Thoughts for next instrument project

The following series of not-quite-random thoughts about the next instrument project:

• 4 strings, maybe 5. Something appeals about being able to cover a string with each finger, as on the mandolin. A fifth string may be useful, but I'll have to ponder the pros and cons.
• Range. With 4 strings and a basic fifths tuning, a range of C1 to A5 is possible; with a baritone scale, this might come off better a little higher, but the point is with 4 strings and a 3 octave fingerboard, one is not exactly wanting for range.
  
• Three octave fretless fingerboard. (After watching this absolutely magical performance, a lot of these thoughts are geared around Manring's Hyperbass.) In theory, a 34" scale would imply a fingerboard of at least 30" in length, a 30" scale would imply 26.5", and a 28" scale, 25" (each of these figures leaves room for the finger to "make" the third octave note). This obviously has implications for things like magnetic pickup placement and the incorporation of such items as a Fernandes Sustainer, which seems to require two pickups to produce the feedback loop. It's quite possible that the Ebow is a better option here; certainly Manring makes good use of it with his light-gauge strings...
• Hipshot Extender tuning pegs for each of the four strings. This should give access to detunings of a m2 through a M3, I think. Would choose guitar machines if possible, for their compact size, but bass machines could work as well.
  
• Hipshot tailpiece with "open tuners" for each of the four strings. This is the device that people get for the "B-Bender" effect, but the design of the part seems to be such that, used as a tailpiece with a separate "open tuner" for each string, may give the quick-retuning option on each string from the bridge...with a lot less complexity and expense than a custom bridge. Will have to check with Hipshot or Stew-Mac to see if this concept is sound, but it's very intriguing and would solve several problems simultaneously, not the least of which is the problem of string spacing across four or five strings.
• Saddle question. With a Hipshot tailpiece, the question of saddles arises. I'd certainly want adjustability for saddle height and intonation, plus string spacing and the problem of friction for the string retunings. Schaller seems to make a "rolling" saddle that might work, and there may be options that plug into the Strat/Tele bridges, but this may require some thinking. Ideally I'd end up with a true four-string instrument, with four saddles adjustable every which way, but with a fretless fingerboard the concept of a singular saddle is certainly viable--and may permit additional undersaddle transducer pickup options.
• Nut material should be lubricous, maybe the Tusq material from Stew-Mac.
• Pickup options will require some more thinking as well. Love the idea of placing multiple transducers in the body and neck. Along with a magnetic pickup, will want to blend this and run it through a preamp, with at least some switching options. Will ask around for opinions, since I'll probably end up making some of this stuff myself. :-)
• Woods, and budget. Will keep eyes open for "found wood" options, secondhand quartersawn necks, etc. This will probably wind up being very much a one-off instrument, but that's okay. My plan is to find something in it that I haven't even thought about yet.