With the large compound leaves that can be as long as 18 inches, Delonix Regia will have to be a large bonsai if you want it to be a broom. With mine, the leaves shade out one another and stunt the growth of the smaller branches so you will have to tend to the tree carefully with a broom because the branches will be close to one another.
How big is your tree now? Mine has a 2.5" trunk and is 24" tall, yet I still have issues with the tree being too small to handle the compound leaves. It looks good in the spring when the leaves are small but when the leaves are fully matured, it still doesn't look right. Perhaps when I get the tree to grow much larger it will be better.