Long travel Fork, air-oil, can have travel left after pumping up the pressure so pre load sag does not take up most of the travel .

but for the riders use 'street and smooth trails', that is over spending .. just rely on the fat tire and stick with a rigid fork ..

your arms are pretty good shock absorbers if you dont straight-arm and lock your elbows.

330 pounds exceeds the weight capacity of the Cane Creek suspension seatpost, so thats Out.

Maybe a super wide tires will do with its air volume in the 4" wide tires

Sun Crusher , comes wit smooth tread Street tires where the Pugsley ships with knobby.

so there is practical options