I would definitely try a retinoid before BP since retinoids are actually GOOD for your skin and antiaging. I would use it if I could, sadly it gives me hair loss BP is actually pro-aging because it induces the formation of free radicals so I would use it as a last resort only.
Also, you may still clear up just from the accutane. I did accutane 2 years ago and was clear for 2 years (acne came back this spring). I didn't actually get fully clear until 2 months after I finished the accutane.
However, even if you do completely clear up I would still recommend you use the retinoid to prevent acne from returning and to help with scarring, and also just for antiaging purposes since it really is amazing for that.
If the acne doesn't clear after the accutane and after 3 months of using a retinoid then I would try the BP. Sadly I'm currently in that boat since I don't want to go back on accutane and can't tolerate retinoids. BP Is very effective though... its just a shame it's not great for aging. But then again, I'm sure constant inflamed acne is even more aging than the BP is anyway!