The "gotcha" with sticking with Ansur obviously is:- what happens if (when) Fluke decide to discontinue support for Ansur, and (as well as) not making any new Plug-ins available if needed for new test kit in the future?
On the other hand ... perhaps there could be an opportunity there for Third-Party Developers (not much money in it, though ... especially considering the time and effort involved).
However ... I should imagine that whatever means are used to insert a "supported device" into OneQA, surely the background code is going to be "very similar" (if not identical) to that of the "old" Ansur Plug-ins.
By the way (as already mentioned), I can see the need for a complete re-write of Ansur. If you look, for instance, at files contained in some of the Plug-ins you can see straight away how they have become not only greater in number, but also increasingly complex since the early days (of Metron QA-90, QA-ES, QA-ST et al).