I'm curious if that would be a reasonable possibility.
Nixie Tubes provide letter/number based displays that are in ways better than just lamps.
Inlaid lamps are, much like your contrast mod, but they cover a little less of each square (At least the version of the mod I use; Inlaid Lamps Extended), which to me is aesthetically pleasing and retains the normal design of regular lamps.

For Nixie Tubes (NT), I would say it may be possible, but I have no guarantee they will still works.
The biggest challenge probably comes from NT is using on_tick updates, to remove and place extra/hidden entity as sprites to display. This adds much more complexity in scaling. (For vanilla lamp, I just have to deal with the prototype. I do not need to care for sprites, control.lua update code, etc.)
And honestly, I do not want to spend triple (or more?) the creation time of this mod, just to support a dedicated mod.

PS: NT uses on_tick event to update EACH of the placed tubes. This is a serious hit to UPS... One of the prime purpose of this mod is to "replace" such mods. Users can design your own display circuits (or just use one of the many digital display blueprints, available on forum). The smaller sizes of lamps and combinators allow them to use much less space, so you can build your own digital display of similar size, which should be faster than NT too. The vanilla circuit signal (implemented in C++) is always much faster than those tricks in mods (implemented in Lua).

Schall Lamp Contrast uses the original sprite sheets and graphics code of the original 0.16 Inlaid Lamps, without modification. (The only change was Pi-C's correction to circuit_wire_connection_point, because he thought it was at the wrong position.) Hence they should display the same as original, I am curious for the difference you have mentioned.

Alright, fair enough. :) No need to fuss with it then.
Nixie Tubes having letter/number display already saves a considerable amount of space over making numbers/letters with normal, non-scaled lamps anyway.
I'll give the lamp contrast mod a try. I wasn't keen on the look of it in the thumbnail, but perhaps it's not so bad.

Thank you for your reply none the less!

Oh, I see why now. The thumbnail is too small (144×144) that poorly shows how things will actually look like. The screenshots of larger sizes within the mod page should give you a much better view. :-)
The "Concrete" style should be identical to graphics "Inlaid Lamps". And I have added the "Black" style for better contrast in display purposes. (Hence the name of the mod.)
There are some other extra options (e.g., adjusting glow size), which is also not available in original "Inlaid Lamps".