mr burinator,
i offer these thoughts only as a person whose experience with these bushes are in the garden not as bonsai or potensai.
the growth on these shrubs in my area (zone 6) begins about now(june) and continues into late august (slowing into september). the growth can be as much as 7 feet for my budleia. you would be one busy person for those summer months, pruning almost daily is suspect. the flowers themselves extend from branch tips and those masses are almost 6 inches in length (not sure how you'd scale them down). the back budding is strong with these shrubs; and in fact it is generally accepted to cut these back to three to four inches from the ground in the very early spring due to their vigourous growth.
i'm by no means saying don't do it, just offering what limited knowledge/thoughts i have on the subject.
best of luck.
bill
