although the above question was asked 7 months ago, here is some comment to it since probably i soon will build qute a few displays which should be quite responsive to show lots of current status data ...
about negative numbers: missing negative numbers are not a big problem if it is easy to see that a number is negative. that could be achieved by adding an additional colored lamp to each number (ugly and quite a lot of additional circuitry), or by simply having a second color for negative numbers (no full color support, but only one second color, eg red tubes for negative numbers).
about general color support: when nixies were new i used lots of colors for fun, and later it was nice to have displays colored according to item types (different colors for each item were done by another mod), but since that once again required lots of additional circuitry for mixed signals (because of color priorities, etc) and because not all items had colors, i stopped using such "colored by item" displays and now use at most green/red to indicate good/bad (eg positive/negative) numbers.
about word displays: some other mods (probably for train station names etc) use encoded text, eg A=1 for A in the first position (I don't know whether this is the first from the left or from the right), B=1 for B in the first position, =2 for the second position, =4 for the third, =2^(N-1) for the Nth position. thus an entire word up to 31 or 32 characters can be transmitted on one wire, eg "A=9 (1+8), B=6 (2+4)" would write ABBA, or "a=2304 (256+2048), e=8, l=17 (1+16), n=512, o=2, s=128, t=1024, v=4, y=32" would spell your name :-)
it would even be easy to scroll the display by simply multiplying or dividing by 2.
and (although not yet tested) there is a mod DISK (https://mods.factorio.com/mod/disk) which stores 512 such snapshots of the state of wires at specific addresses in its virtual memory, ideal for storing up to 512 notes of a song (to be played by the speaker) or for storing lots of encoded text (up to 512x32 characters = 16 KB of text !!!)