Can the Release Managers suggest a calendar for raising those bugs,
first to important, then to serious?
What I had in mind was that you'd file the bugs and after some time (say, one or two months) raised them, giving maintainers a bit more time than usual to react to this novel class of RC bugs as you've now started to actively test. I consider these bugs RC as they will exhibit themselves as FTBFS during the stable release support period. So I suggest you mark these bugs as RC now, such that they can get fixed in time for the trixie release.