I love the Exmoors and the lambs are pretty decent lambs
And best feet in the business, according to Richard Webber.
They are not a listed rare breed, just geographically sensitive - so if you were
outside the area, I'd press you to have them. But as you are very nearby their main area, and the Whitefaced Dartmoor
is a rare breed, then perhaps the latter is more needful of your support.
However... I have two longwools here for the first time and I do
not find them just the same as any other sheep to manage.
I do not like Clik or Clikzin as it is so environmentally damaging, but I think, in a warmer summer, I would have no option but to use it on my black Wenseys. Crovect only protects the wool you spray, whereas Clik and Clikzin work more systemically. There is so much wool on a longwool, even only a few weeks after clipping, that I don't think I would feel comfortable relying on only Crovect in a bad fly season.
Also, being a wet farm here and very high rainfall, my Wenseys were fairly miserable all last winter, despite having been dagged hard in the autumn. I plan to take a second clip, leaving them an inch or two of wool, this autumn, and if they are still miserable this winter then I would have to keep them indoors (or in the home paddock with a stable they can use), and/or sell them to somewhere drier.
Re: your plan to use your local breed tup to cover some of your commercial ewes... If you use the Exmoor you may get horned lambs. If you use the WFD then you'll get a lot of rather course wool! Exmoor cross would look more 'normal' in the ring, I suspect, although the horns might give the game away.
(And the coarse wool of the WFDx would be unpopular in the ring.)