I doubt any airframe manufacturer certifies their aircraft for flight in IMC. For flight under IFR yes, but for flying near a cloud??? (depending on the airspace)
Equally, without wishing to be pendantic, I choose the term carefully. Aircraft are certified (or not) for IFR ops., but IFR in VMC is no different from VFR in VMC. VFR and IFR refer only to the flight rules not the met. conditions, but the presumption is for IFR ops at least for some of the time you might be IMC. It is for the reasons of the met conditions, not the flight rules as such, that the instrumentation requirements are different.
I dont agree that the conversation is only relevant to high level. In fact the risk of a collision is far greater at low level because there is more traffic.
If you are willing to permit flying machines to operate without any commonly agreed means of identifying their position then you might just as well permit pilots to fly around with foggles or screens in VMC (sans safety pilot). In both cases you have removed any chance of see and avoid working.
IO540
You have a point, but as you know it is often inconvenient to fly airways, particularly on short legs. Often CAS restricts the aircraft to a corridor above the base, but in IMC below CAS. The options are to scud run or continue IMC in the corridor. There in lies the real risk of colliding with a glider that is transparent to air traffic and every other user of the said airspace.