Welcome to site!
Lots of great guys here to help.I am more than glad to help you if I can.
Unless you have access to a press brake to form the ripple bends in the top I would for gore that plan.Too many seams to weld for each ripple.
Now I would build a fire box with flat sides and octagon shaped to some point. heat transfer happens faster on a flat surface than a round surface.
I would then go and study different design stove exhaust passage designs.I am a big fan of how the Portage and Mains are designed.
they have access to clean the exhaust and are double pass to extract heat in the water jacket.
I would definetly go with an blower.I like to the fire to pick up fast and start producing heat,rather than lazily stoking back up.
I would use your 1/4" for your fire box.Then get some 1/8" or 3/16" for your water jacket.I used 10 guage.Heck water tanks and oil tanks aren't that thick.
You could build a stove like mine.You would actually be way ahead if you did build a gassifier.They use less wood and smoke alot less.
Don't put that option out yet,You will find that after you build this once you wont be in a big hurry to do it again.
Make lots of drawings and try to keep track of the big picture of how everything works together.Always be planning 5 steps ahead.
take your time ,and think out every step of your build.
good luck,and oh yeah take lots of pics!