Here's a problem $COST$ most quality items are made by big name brands! If you could manufacture say a stable, light canister stove of your own! Thats capable of boiling efficiently water as well as simmering at a fraction of the price. Say half of the average marketed price. And the item be of the Same quality & let's throw in made and assembled in the USA.

Then My Friend you have identified and created a solution.

Otherwise there are plenty of nice stable stoves out there if your willing to pay for them.

But I'm with Lori even on mountain sides its usually not to hard to improvise a bit of a flat spot. And if your truly in a situation were a flat spot is Improbable . A lot of stove manufactures make hanging kits