personally i more like enjoy others NAT-T things support in RouterOS, but if anyone be happier with NAT-PMP its okay, WHEN/IF someone implement relatively secure support of it, which is not happened, yet, sadly
and since NAT-PMP mention - why not PCP instead, which is ough to be replacement for NAT-PMP, right ?
ie, This thing
https://en.wikipedia.org/wiki/Port_Control_Protocol
its support EAP and other essential features and thus resolve portions of concerns/flaws both security and performance -wise.
and yes, it May be useful. just like DIAMETER implementation along with RADIUS its ought to replace over time/years.