What would be a good workout (strength and conditioning) program for a fighter the 4 weeks leading to a fight? How intense? How would it taper down towards fight date?
Depends on how much of specific work he is putting in - I would put in much sparring and hard specific training. But that's a toss up because of the bigger injury risk.
You really wont achieve a massive in such a short time, id stick to bodyweight exercise or barbell complexes up until around 10 days out, depending where you're at with weight, sparring etc.
Once the fight is done get on a strength program Westside for skinny bastards for example, so you have a better strength foundation for next time.