Thankyou very much for replies to Wolvenar and Ghurd. I'll source thatkind motor like Ghurd suggested when I have more time. I have been busy for repairing cars, tractor etc. Seems everything broke down nearly simultaneously so haven't had time for this most intriguing hobby project.
I discussed about that motor conversion briefly with my brother in law who happens to be an electric engineer & designer. He told me pretty much same things as you did. I have a very small (around 350 W) squirrel cage brush motor from newer washing machine which have 2 large coils in stator side and inside rotor have pretty many thinner wired coils.
I originally thought that would be perfect because it is very lightweight. So perhaps I'll make a try for that with the following idea:
1.) I strip the rotor windings and brushes away. (possibly reuse the copper wire aiming for 48 Volt windings)
2.) I bore rotor holes for magnets (4 poles, 2x4 magnets in each)
3.) I make a mold for coils from PVC pipe to outer side and thinner material like big soda bottle to inner side diameter adjusted & patched with silicone to prevent leaking
4.) I cast the coils with 2 component polyurethane
So this design is pretty complex in a way but could be very lightweight and I could easily fit coils. So coils would be in circular format and magnets in rotor.
I have around 14-16 meters 63 mm diameter very hard steel pipe, thickness 3+ mm (ex professional welder said they are made of excellent steel quality) and it's zinc coated (all ways remove zinc coating from welding area btw, very toxic to breath). I am planning to make from them the test tower. Pipes are about 4 meters long and I planned to weld bolting plates to them and bolt them together. Also a guy wire tilt tower design because this would be a test bed for my tinkerings.
EDIT: corrected some of typos, my english is pretty rusty like my motors