I would say stick with a pressurized system, if nothing else, it will be cheaper.
100 gallons is way to much, 50 gallons in a hand fired and maybe 30 for a stoker max unless you are building a monster.
The forced draft is good for recovery as stated but does blow your heat up the chimney. If you are looking for some good natural draft controls, check the TARM, Burnham Woodlander and I think Energy King each have nice working natural draft control. You can find out about who makes the Burnahm draft regulator by PMing member Cheng_Baugh as he has a Woodlander. I believe it is the same control as was on my circa 1900 SEARS furnace I had back in the '80s. One thing is for sure, it won't wear out and will never fail when power is interrupted.