This is quite possible, check out the map duel_octagon_b1:
http://www.fpsbanana.com/maps/42666
Not much to look at, but does exactly what you describe. Somehow records a player death and marks the number on a scoreboard.
Oh...well apparently the map is protected from decompliling. Clearly it shows that this is possible however. My guess is that it simply has 10 boards for each number place (so 10 for the ones, 10 for the tens, 10 for the hundreds) and turns on/off the appropriate board when a death occurs.
So i.e. would start showing 0_hundred, 0_ten, 0_one to display 000.
When someone dies a math_counter for the ones place would add one and send that info on to a case_logic that would say:
- InCase01 TurnOn 1_one
- InCase01 TurnOff 0_one
Now it would show 0_hundred, 0_ten, 1_one to display 001
The InCase10 would have to reset the math_counter for the ones back to 0 (thereby display the 0_one board again) and also add 1 to a math_counter for the tens spot.
So the upon ten deaths it would show 0_hundred, 1_ten, 0_one to display 010
I tried to make that simple sounding but i might have just obfuscated the point. Hopefully that makes sense. Oh and i remeber your sketches from the TF2 forums. Was an amusing idea then, still would be interesting to see it play out. Probably would require lots of custom textures to make it interesting, but a road-side diner like that would be an interesting locale.