Do you know what species this is?
Honestly, if you're really wanting to collect this and start developing it as bonsai, I'd be more inclined to chop it down to one of those lower branches at the base. I don't really see a nice bunjin here, TBH.
Depending on the species, what the base of the tree looks like, and the arrangement of those lower branches, you might have the making of a nice, smaller tree. You'd just be considering the stuff above it as a sacrifice.
Can you clear away the base and take a picture of the lower trunk and those branches?