old bougainvillea trunk

[GHASEMI]

Ghasemi]
Hello Friends
Thanks all for your useful information about bonsai sharing with others.I recently given this old trunk bougainvillea, planted on a small pot. this bougain had been detached from mother plant about 2 years a go ,as i got it, checked the soil which was only sugary sand in a 4 inches pot,fully wet because it had been in rain for long time.I changed the soil and planted in one size bigger pot ,the root is too hairy formed circular at the outer age of bottom of trunk . i think the round shape of bottom of rooted trunk shows that this old baby is a cutting trunk which rooted.the plant height from pot soil is 6", trunk diameter at plant base and in middle of trunk both are 4.7"and at the top where the branch comes out is 5.7," there is a long and deep scar in one side of trunk as seen in one of photos.please give your advise or design to start with if this plant is capable of being bonsai in future or is better to transplanted in my backyard garden. Appreciated for your guidance. Best Regard Ghasemi