Wow, T41748 looks really complicated...
This attempts to be a simple and working solution. Yes it uses bmesh, but the other modes of this modifier do so, too !
Unless you really have big meshes or many of those modifiers in the stack i dont think the performance will drop
so that the viewport will stutter. And removing verts effectively gets rid of all other elements too like edges and faces.
On the other hand you get a workable solution here which might come in handy in the real user workflow.
For example this might also solve T47334 indirectly, by putting a decimate / remove doubles modifier after each solidify modifier.
Even if its not the "nicest" and "best" and "most optimal" solution, it just works. And that matters.
Realize this can be useful but its not really belonging as a decimate option.. (remove doubles with very large values doesn't give deterministic results).
For now closing this... the feature its self can be useful in some cases,... but rather not add this right now and instead hold of until we have nodal modifiers and can investigating having fine-grained edit operations chained together.