If you get a Charollais that has wool on his head he’ll throw lambs that are better covered. In every other respect they’re exactly what you’re looking for.
We had two in Cumbria, outdoor lambing from Texel cross (and Lleyn cross) ewes and only had a very few really bare lambs over five years of using them. They are born easily - the smoother skin means less friction - which translates into easy lambing and very active lambs. So they get up and get milk quickly, which makes them warm quicker than Texels or others.
In bad weather we would (and not just when using Charollais tups) get out and jacket any newborns that had other than a really thick coat (usually lambs born to Mules) and I can’t think we lost Charollais lambs to weather any more than we did Texel lambs. Probably less in fact. (The latter can be a bit dopey and slower than the Charollaises. I often thought this could be in part that being more muscular at birth, they had a slower more stressful birthing which took more out of them.). I’m sure we jacketed a higher proportion of Charollais x lambs than we did Texel and Beltex x lambs, but the lambs did so very well we didn’t mind the cost of the jackets!

. (And unless it was evil cold wet weather, none of ‘em needed jacketing.)
I would have thought Charollais on Lleyn would be a dream cross. The Charollais lambs grow like billy-o, always weigh more than they look; the Lleyn produces gazillions of milk off grass - wowzer.

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If you’re still concerned about thin skins, you may be able to get a Charollais x Beltex tup. (Beltex would be my second choice for you if you didn’t “despise them”! ;p). )
I’ve no experience of Berrichon but from what I hear it would suit your situation. How the lambs would sell I’m not sure, and I don’t know about growth rates.
Lonk is a hill sheep, totally not what you’re looking for.
One other idea... I’ve used a Romney this time and the lambs are super. Fab shapes. Too soon to talk about growth rates but I’d expect them to do well.