Ferment a mash then purée! Ferment a fruit at the same time or just blend one in afterward like a pineapple. Hot and sweet usually appeals to the most people.

+1 on lacto-fermentation. The taste is pleasantly tart because of the lactic acid, but much more agreeable than vinegar IMO. It keeps for months in the fridge as well.

I would not use molasses personally, might taste too strongly and darken the sauce more than I want. A bit of honey could be interesting though. Cooked sauces might retain more of the pepper's sweetness than fermentation, since the bacteria eat the sugar, but I find it fine as is. I've finished a batch with a bit of pineapple and it nicely added that extra bit of sweetness.

Use bell or other sweet peppers to cut down or control the heat level if using pretty hot peppers and not wishing to make a scorcher of a sauce. A bit of onion or garlic can round out the flavour profile as well.

+2 for fermenting :) I've used molasses in sauce before and it came out fantastic. A little bit goes a long way though. Come to think of it, I used pineapple AND molasses in the same fermented sauce, haha. Color didn't matter much since Douglahs and Chocolate Scotch Bonnets were the base. Everyone seemed to love it.

This link might help: http://c2cpeppers.proboards.com/thread/1464/fermenting-peppers