While LT has one of the most complex positioning systems for sex, i find it also very frustrating to use for 3 reasons:
1. Changing from one positioning-setup to another takes far too long, mainly because the standard button interface is slow and inefficient, when there are more choices than buttons per page.
2. It's not at all obvious, which actions are possible from which position.
3. Partners - even allies - constantly interfere with actions (read: they block your actions. I.e. she's already fingered bby someone, so you can't fuck her). While this can be turned off manually, doing so again is slow and frustrating, because of the above mentioned limitations of the standard button-interface. And one has to turn it off manually for every single involve actor, AND it costs one turn per actor.
Combine all three of the above, and you get more than the sum of the parts (in a bad way). I have no real solution for #3, other than player actions automatically overriding those of others (especially when you're in the dominant role).
For #1 i think sex-positioning needs a dedicated custom interface. #2 can build right on such an interface, by displaying which actions will be available, while you configure a new position.