File IFR for RIS/RAS
I have an IMC rating and file IFR quite often, even OCAS and VMC.
The reason is that (assuming there is radar coverage) I find that giving "IFR" as flight rules instead of "VFR" gets me RAS or in most cases at least RIS when all the VFR aircraft around are getting FIS.
May not help a lot in avoidance, but having a RIS/RAS seems to me that I am likely to get a bit better attention on the screen than the FIS folks (and does seem to work this way, comparing when I have a FIS with RIS/RAS).