The idea of non-forced, non-exclusive, Marches is itself a really cool idea. (One that would be interesting to see all houses adopt some form of to maintain some kind of voluntary associate and shared control of the border worlds.) It has the potential to lead to a lot of really fun and organic roleplay between houses/pirates/militaries/etc.
If it had come from any other house, or even BretGov at any other time, I think everyone would like it.
But that's still kind of a problem. It wasn't proposed by any other faction, or at any other time.
However, The idea of BretGov shrugging off the current issues could itself lead to some organic RP between them and LibGov/LibCorps. Maybe it doesn't need to get reconciled to move the story forward. And rather than using the issue as a revolving pissing match the sides involved turn it into an inRP conflict. Since DSE was the primary victim of the recent shenaniganry, (retconning the law after the fact doesnt erase that from being true.) DSE could petition LibGov for reconciliation and that might turn up the already warm tensions between Bret and Lib, and then that's just that, maybe LibCorps start disrupting the Bretonian Marches or paying Bretonian pirate groups to do it for them. Then that leads to a more publicly accessible reason for the Lib/Bret tensions turning than some obscure debt/treaty crisis.
Maybe the current distrust some factions have for Bretonia (either legitimately or illegitimately) fuels other Houses doing their own rush for Marches. Could be fun.
I guess the main issue would be being able to drum up enough activity to ensure that the Houses could actually back up the agreements they make with indie PoB owners, to actually keep them supplied and defended. Though I suppose if Bretonia cant, then PoB owners could always seek agreements with other Houses if the other Houses actually parrot this idea.