He said no to the electoral reform proposed… and he cited the insistence on MMP on the left as evidence they weren’t willing to compromise. Thus, there is the possibility that a new mixed form could enable reform. It is 1/4th+ of what he wants and it would tend to let his party either have a majority or be the biggest party in a coalition, which is what he really wants. However, presuming he and his party prefers to have a majority, it’d force him to be more mindful of minority groups than they would if it was AV alone….
And, as you pointed out, the vulnerability of FPP to whisper campaigns and gamiing of the system by the CP is reason enough to seek out new hybrids that might be more fit…