my main reason for doing the IMC would be so that I can still fly on the decidedly marginal VMC days
I would say that is not a good idea, even for a relatively experienced pilot. Others much more experienced than me will tell you that flying in IMC for an extended period is a hell of a strain and you really need an aircraft with an autopilot to reduce the work load. Not only that, in winter you have serious risk of airframe icing in and often below cloud.
I use my IMC to get above cloud where I am as certain as I can be that I can go VMC on top and that the cloud base is not likely to deteriorate to a point where making an instrument approach is going to be difficult (because of the minima for IMC rated pilots). It is also very useful training for those occasions when you enter IMC inadvertantly, but even then I descent to VMC unless it is obvious that the IMC is very temporary.
Flying is more enjoyable when you can see the ground. I would not set off in 'marginal' VMC unless I was very confident that the weather is improving or it is or will very quickly become VMC at my destination.