Well, that idea was already suggested (maybe was even you ?), but put in this way, it would work only in the situation with Myriam DOM.
The equivalent alternative for the Myriam not DOM (assuming of course there is sexual activity between Myriam and Marc, remembering it is completely optional), could be Marc actually wants Myriam to do it, getting off at the idea that "his bitch" is really being a bitch for Cassius, or just catch her in the act looking at it, and in both cases eventually may even join in to enjoy "his bitch", of course after taking a video ;-).
Reminds me of an old video I had seen on the Internet, coming from a VHS tape made in Denmark, and believe or not, the dog and the man where sharing the girl at the same time.
Which on the other hand could open another possibility, already mentioned, not with Marc but with the veterinary, either with his dog, of if the veterinary is so good with Cassius that Cassius decides to share Myriam with the veterinary and/or his dogs).
Let's just say if Zolrun wants to add up another scene to make the fans of Cassius and Hammer happy he has plenty of ways to do it, though for sure he needs to take care of Finn and of the volunteer activity, by his own words, and it is to be seen how much stuff he can put in one update.