Sound-from-Scratch Microtunable Synth Recommendation?

This general topic has come up many times, but I'd like to pose the
question again in a manner most directly applicable to my immediate task at
hand.

Do any of you folks have recommendations for your favorite synthesizer
capable of building sounds from scratch, and also having at least one
user-specifiable completely arbitrary tuning table?

By "building sounds from scratch", I mean something like FM, or the ol'
Moog-style analog, as opposed to minor tweaks on sampled sounds. Or even
better would be something that lets me do Moog-analog style filtering
(etc.) on FM-generated sounds. Now if it has a set of samples to build
from as well, then that's all the better, but the scratch-building
capabilities are especially interesting for what I have in mind.

And by completely "arbitrary tuning table" I mean one that lets you
assign any pitch within the range and resolution of the instrument to any
key, completely without regard to what pitch you assign to any of the other
keys (e.g., no requirement that they pitches be consistently the same
distance apart, or that there be any octave repetition). Not surprisingly,
it would be vastly preferable if the machine had a means of storing away
these tables as well (i.e., that I don't have to send it SysEx messages to
regenerate the table everytime I power it up).

Suggestions? Thanks!