Why are you in IMC?
There might be a good 2,000 feet between the base and the ground. You might be a few hundred feet above the base. You might be there because you want some experience of flying in IMC in relatively carefully chosen conditions - no convective activity what so ever and no risk of icing. If things go wrong there is a readily available out. For a pilot qualified to do so I don’t see that as unreasonable. Moreover I don’t see it matters whether or not there is water below - if the same pilot was also happy to fly over water in VMC.
A wholly different scenario is flying IMC with low bases, embedded activity or icing. I think these are a no go events in the average SEP which is not equipped to deal with these conditions. The minimum equipment in those circumstances is a decent nav fit, storm scope, de-icing and, for low bases, an extra engine.
With any system surely a reasonable starting point is redundancy. We have two VORs so that when the first fails there is a second. We have two fuel pumps or a vac and an electrically driven AI for the same reason.
Having one engine does not seem to fulfill this criteria. However, in fact it does. If it fails we have our eyes and an aircraft that performance in a way that the chances of a successful FL are pretty good. If the engine fails in IMC, with a low base, you are down to one system. Your eyes are useless when you break out at 500 feet - all that remains is luck. With a base of 2,000 feet the second system with a lot less luck has got a reasonable chance of doing a good job.