On top of other suggestions (and there's a good trade in Curry Nights in a lot of places), what I think would be good is if there's a place where people with allergies/intolerances can be sure the food is reliably safe to eat. I don't just mean in terms of nuts or seeds or the new regulations, I mean things like;
Dairy Free - no milk in the burger buns (so bin the sodding brioche) and the ability to ask for vegan cheese without having to pay the best part of a tenner for a flat mushroom.
Gluten free - no breadcrumbs in the sausages, burgers, the mustard (yep, premixed Colman's has gluten, mixing up your own from the powder doesn't), using cornflour or potato flour to thicken stews, not putting all burgers on buns as a matter of course because 'can't you take it out of the bun?' isn't making it gluten free, if you serve chilli (meat or veggie/vegan, just have tortilla chips that are gluten free for everybody, as no one will notice the difference except for celiacs (because they can trust them). Same with poppadoms instead of Naan - get GF ones for everybody - obviously Naan isn't GF, but why put the poppadoms out of action as well? Not buying in chips that are coated in flour. Being able to have something in breadcrumbs that is GF would be great - like fish and chips, Scampi and chips, etc.
Don't confuse needing to be GF/DF with being vegan. Because that makes for the worst of all worlds.
With the margins on food, it would be pretty easy to plan into pricing so that nobody is penalised by having to pay more for less in order to eat safely - Spoons' vegan curry is about a teacup's worth, but costs as much as a huge curry full of dairy and gluten as thickeners, for example; which is pretty shit for those who can't eat anything else on the menu.
Essentially, where a substance really doesn't have to be in a meal, make it easy for it not to be there and normal for somebody to be able to order it without being told 'oh, we're out of that' and I think that'll also get a dedicated bunch of regulars eating there who just can't trust the other pubs in the area.