It is reasonable in principle; the question is how it is feasible. Most of what "the FSF does" is done by volunteers. Would you like to help?
Over the course of 2014, 2015, and 2016, I tried working with RMS to get him to patch things up with Miguel and issue a revised edict on the use of .NET and (ridiculously enough) the entirety of the C# programming language.
He hemmed and hawed and over the course of those conversations even suggested that Microsoft re-releasing .NET under the Apache license might not even be sufficient for him to retract the fatwa.
I suggest that someone take RMS's statement here as a mandate to declare that .NET is now hereby recognized by the FSF as sufficiently free, to prepare "GNU .NET Runtime", "GNU Mono" packages, and announce a victory for free software.