is there any mod that allows to go beyond slider limits?
I don't know about one and I doubt that it exists.
It's possible to change size beyond limits via
Cheat Engine utility but that's problematic from at least two reasons.
First is that antivirus software doesn't like it and second one is that those sliders generally limits size so that results work in game. If some body parts are too large then they doesn't properly work in animations.
There is possibility to make models shaped differently via bone system so one can make basic body parts larger in the first place. Sliders still work but now with larger body parts as starting point.
Problem is the same as with Cheat Engine and body parts will not work properly.
But it's not entirely impossible as demonstrated in this screenshot with two Mayas, both with butt and thighs sliders to the maximum but one with larger ass via bone system.
This version also works reasonably well in animations.
I found that tits are much more difficult to enhance and my versions unfortunately doesn't work properly in most animations (at least with sliders to the max) but maybe someone is more lucky.