OTC can't be considered "protocol 8.6", the whole point of 8.6 ots were to be able to use elfbot, that is like the 99% part that made the 8.6 client "successful", if elfbot stopped at 8.7 version, trust me, it would be the most "famous" version and any other you could imagine...
now back to the topic, my opinion:
instead of the hassle of adding new content to "8.6", just move on already and do a 12.50 server