southpaw here. ive been practicing my opposite stance for a few weeks now, not bc i want to be a switch stance fighter, just to avoid being a fish out of water when i do end up in the opposite stance.
some things i've noticed: in my original stance, 60% weight is on my backfoot. when i switch stances, it ends up 60% weight on that same foot which becomes my lead. that makes me fight differently, whereas when im backfoot dominant I use a lot more front leg teeps, front leg kicks. now with frontleg dominant i do more boxing and less kicks. I'm not sure what other consequences are there when I switched frontleg to backfoot dominant. I've been trying to correct it, but maybe it is something I can build on (if I want to focus on boxing, i switch stances, something like that). probably not though xD
there are more weapons though if you can do opposite stance momentarily. from orthodox the switch kick is way more useful. the outside right kick which is just a constant nuisance in southpaw becomes a power weapon. and all your left kicks are still power, you just shift into it which i personally like doing from orthodox.
there are a lot of problems im facing though, bc i havent gotten used to it. in orthodox i sometimes feel like a one-handed fighter, bc i rarely use the cross, its only used to setup my lead hooks and uppercuts. like fullmount said, most stance-switchers suck. i think that may be because they dont put enough time into either stance. so instead of being 80% good in orthodox stance by focusing on one stance, they end up being 50% good in orthodox and 30% good in southpaw haha
EDIT: Went back and read a guy's overview of positioning thread. a lot of things he mentioned were exactly how it is, especially the cross being sucky if you're front foot dominant. i end up bending my spine to get the cross out instead of rotating well.