The rating (trueskill) is made to define the skill of a player, hereby its possible to host well balanced games - making things predictable...
Skill includes the ability to do as much things as possible parallel. To compare peoples skill it is necessary to give the rating system a CONSTANT! This is the gamespeed, or the defined properties of the unit (buildpower/dps and so on) or the engine of the game or the economy system.
If you take one of these constants and make it variable you can't compare the skill of the players anymore - THE RATING WILL LOSE A LOT OF SIGNIFICANCE. This is the reason why all the other mods, some special settings and so on are not included in the rating system. You get more and more variables which can't never reduced to a common denominator.
For example:
A player who played only -3 games and reached a rating of 1900 is never comparable to a player with equaly rating who has played only 0 speed games. If they would play a game against each other at 0 gamespeed, they wouldn't be on a same level.
That's the same with players who only play No Air, No Exp, No Rush...
All you can do is, set the gamespeed to -3 or -5 constantly. That means, force ALL the players to play at low speed. But this won't happen definitly/hopefully.
We know - 0 game speed is sometimes hard - especially on a ressource-rich map in an 1vs1 situation - you need to do a lot. One big advantage is in those situations you can try to overrun your opponent or distract your opponent or whatever. In a slow game these strategic options aren't viable. Your opponent will see nearly "everything"... thats why the mandotory don't like it apart from that it takes ages to end a game.
If you don't understand what we tried to tell you, than read the wiki -> trueskill.
I'm not sure, if you already understood that.
If you just wanna have an award or something for your wins against the other slowmo-noobs - than start a regular tournament or whatever.
Or better
... adjust your cpu multiplier to a low value, that you just have 1.4 Ghz or something. Than you can play ranked games at a very low speed dude
It has a reason that the gamespeed is fixed for ranked games!
Otherwise we could include minesweeper and tic tac toe to the rating system as well