Someone in this subforum bought a SS2 and loved it. I believe they posted in the Surface Devices thread. My only complaint is the old internals for the astronomical price (which is also true about the iMacs).
If the SS2 was available for $3500 maxed out, I would happily jump. The display is gorgeous and it seems like a very good machine.
I don't think you're crazy, but if it was me and you could hold out until later this year, I"d wait. MS might release the SS3.
I have seen some YouTube channels about upgrading the RAM and the harddrive to SSD in the SS2. It seems relatively easy to do (only screws in the base). But, you are right, if the OP wants to buy a new SS2 it can be sensible to wait for the SS3.
It depends on the price of the SS2/SS3, but (even for the same price as an iMac) for graphical design it seems to have advantages over an iMac (touchscreen, pen, easel-like screen etc.). With the iMac there are extra costs for a drawing tablet (Wacom?) etc. which is not exactly cheap either.
For some people (maybe also the OP) MacOS vs Windows can be a reason to stay with the Mac though. In the case of graphical design however, 99% of the time is spend in the graphical design programs. In my opinion the OS is less relevant in this case.
Edit:
Sorry
@Shooby101 that I am speaking about you in the third person, but that is because I was answering
@kazmac