jdryyz said:

But isn't AVCHD native to Blu-Ray? I would think I could do the .mkv to AVCHD conversion then simply burn the AVCHD data to a BD25 disc with no loss in quality. Am I missing something?

Terminology problem. AVC is a video encoding. HD is high-definition video. AVCHD is video encoded using AVC in HD and then burned onto a DVD. If you plan on burning to BD-R, there's no reason to even talk about AVCHD. When you say the word AVCHD, people immediately jump to the first step of how to compress the data so that it fits on DVD media.

Converting the MKV to burn to BD-R is trivial. Demux the streams using MKVtoolnix or somesuch, and then use tsmuxer to put them into a Blu-ray compatible format. I've already done this.