From a mechanical point of view you need enough gap for the magnet rotor not to touch the stator. That depends on many things including the type of bearings and the rigidity of the whole generator assembly. I have got away with 1mm but with other forms of construction you may need larger,
In a very high wind area it may be wise to have 2 or even 3 mm if you overhang things on allthread with the gyroscopic forces.
For a high wind area if you are following a common design you may not be advised to use too much clearance unless you use a higher magnet grade or bigger magnets . Large gaps mean running at higher speeds away from stall and you will have to be careful to get it to furl early enough.
You say things will get hot, yes that is true but you must make sure they don't get too hot, if you can't make it furl at a safe power level it will die. It's up to you to make sure you can control it and for your wind area I personally would use far more magnet than normal, thicker wire and make sure it doesn't get too hot. If you want to use a brake switch to stop it during the worst storms then you will need lots of magnet. I wouldn't attempt anything for your extreme winds without having a reliable independent shut down mechanism but that is just my personal view. You are likely in an area beyond survival for many commercial units. If a self build machine is to stand any chance of survival you need to give it every possible chance.
I don't know how much coils expand, I have never run anything hot enough for it to be an issue but I think burn out will be more of an issue than expansion and loosing the air gap. Once the thing gets too hot and the wire deteriorates and the resin gets soft the coils will deform and that is not the same issue as expansion. Things will not run for very long at the temperatures where deformation and wire damage takes place. I know some are pushing these things to near class H temperatures ( and likely beyond at the centre of the coils). I see no prosp[ect of any reasonable life if you do this.
I personally don't think the common resins are suited to working over 100C but many are doubling it so it depends on what you consider a reasonable life. On the average site the duty cycle is probably not much over 50% but if you have winds over 100 mph it may reach 100% and that is a challenging condition.
Flux