I would not recommend feeding rabbits to BP's for two reasons.
First, BP's eat African Soft Fur (ASF) Rats in the wild. They generally do not get over 90G. This means a small-medium rat is an ideal size for a BP.
I gave Shayna, my female BP, medium rats and she often refused meals and went on hunger strikes in the winter. When I switched to small rats (60-90G vs. 100-130G for mediums) she began showing more interest in feeding and barely skips a meal or fasts in the winter. She also put on a little weight. Eating smaller meals regularly is better for BP's than larger meals less frequently.
I have heard similar stories from other keepers. Even XS Rabbits are .5-1lbs. That's about 220-440G. Your BP would have to be 9-10 pounds (4kg+) to make an XS rabbit worth consideration, and even then, it would be a big meal for one. They are not stretchy and should not be fed a meal bigger than the width of your snake.
In contrast, Boas like BI and BC can eat larger meals less frequently. Additionally, larger rats have higher fat content and that can be detrimental for boas who do not digest fat well. A large rat is as big and fatty as I want to go for Behira and feeding XS rabbits will give her ample protein and nutrients without higher fat.
She also weighs about 9 pounds and is over 6ft.
Secondly, BP's tend to imprint on prey items and can be difficult to switch when they find something they really like.
Some won't switch off mice, or will, but not easily. I have heard of keepers who offer ASF rats to get their BP to eat (when refusing other prey items), but then have great difficulty switching them back if they want, or if they cannot find ASF's, which is not unusual. They can be hard to get.
If your BP is happily eating rats now, I would keep him or her on rats.