The new regulations lumped everyone into the same category, which they should never have done. In the past, if marriage or common-law status occurred "after" your COS date, there was no entitlement to SE benefits, except in the case of Married Service Couples. For MSC's, one party was automatically entitled to the benefits of Low Rate SE but as it stands right now, there is no entitlement.
When you think about, if you married a non-military member, it is entirely within your ability to relocate them to your current location. But in the case of married service couples, you cannot relocate either of the parties and this was deemed to be as a result of "service reasons", hence, the automatic entitlement to SE benefits.
It is definitely an issue which needs to be addressed and hopefully it will be, sooner rather than later. Nevertheless, the op should submit a request to their supporting URS requesting Low Rate SE as part of a Married Service Couple and your supporting URS should be smart enough to staff the request to DCBA for review.
As far as the issue of common-law status is concerned, once you begin co-habitation, the clock starts ticking. If your partner is also military and one of you is posted prior to the 12 month cohabitation period, then the clock should "reasonably" continue to tick. I have seen a case such as this in the past and CL status was granted. Why did DND pick 12 months? Who knows, possibly a mean average based on the various provincial laws across Canada or to prevent rampant CL requests. Nevertheless, I have also seen individuals cohabitating for short of the 12 months, get a posting instr, request CL Status, have it denied by their CO, then request a JAG review, resulting in approval.