All brachychiton back bud well.
In the past trees on farms were lopped in times of drought to give the livestock vital feed. The trees all grew back after lopping off entire branches.
Leaves do reduce but you are starting out from quite a large size so don't expect minute leaves on bonsai. Leaf shape changes as the trees mature. Juvenile leaves can have thin, spidery lobes but adult leaf generally has wide lobes or simple with a pointed tip.
Seedlings usually develop a large, swollen root below the trunk which can look daunting when repotting but I've chopped some real hard and they just grow new roots.
Repotting and root pruning seems to be much better in warmer weather - late spring through to middle of summer is recommended here.
Brachychiton sp are all frost sensitive. B. populneus is the most cold hardy and can cope with light frost but over there I'd probably treat it as almost tropical.
