Well, another approach is to ask the BYO questions before the ACBC as separate select-type questions, not do component-based summed pricing (specify price as an over-arching regular attribute, or as a summed-price where only the base price is the component that varies).
In that case, oversampling of BYO levels will not happen in the ACBC survey. Each level will be sampled roughly equally per respondent. But, you can re-introduce the information captured in the select-type question version of the BYO questions during HB utility estimation as customized utility constraints. There is a section in the ACBC help manual about custom utility constraints in HB for ACBC. That way, the preferred level from the BYO questions will strongly be influenced to be the preferred level in the final utility estimation.