There are (were) a few companies around years ago who'd do sierra cosworth conversions in the fiesta which could be rwd or 4wd, I've actually seen a MK1 fiesta with a rwd conversion.
Like it's been said you can do it but to do a nice job it'd be best to use Renault parts otherwize it's just a kit car with a clio shell (well, that's the way I look at it) if it is renault throughout, I can't think of a readily available 4x4 renault which'd be any good to use as donor and provide enough poke to be worth doing. And I dont like twin engined cars.
I helped put a rover v8 in an mg years ago and learned then how much work is involved in what I would regard as a fairly simple job. A 4x4 clio would be awsome but not easy or cheap to do.