Recntly read the program of swedish WSM competitior Johannes Årsjö and it was similar to what you suggested btb. He worked his way up on the deads and squat to 1-3 heavy sets of 5, and that was it for the big lifts.
He also mostly does frontsquats (only back squats if that's a part of an upcoming comp, or if its possibly he will have to do it at a comp). The reason for choosing front squats were that they dont tax the lower back as much, and that they carry over good to
atlas stones and other movements involving the core and legs.
He works alot on clean and press (barbell or log).
He gave some tips on how to do improvised strongman training in the ordinary gym - Put 45's together with ropes or straps to simulate stones or kegs, do the yoke with a loaded barbell, farmers with db's.