Again, what constitutes "buffet" will vary from aircraft to aircraft. I don't think it would be fair or wise to characterize the buffet boundaries as safety zones or to make assumptions regarding what one may encounter beyond, or the ease of recovery. While certainly one may be able to get slow and recover, it may require considerable altitude loss to do so (many thousands of feet, for example). In RVSM airspace with little margin of separation between aircraft, the recovery alone could present a substantial hazard not only for the slow aircraft, but for other traffic as well.
You brought up the example of a light airplane getting slow. You may find in one airplane that as the airplane slows a buffet occurs. You may get vibration from the horizontal stab, you may get rattling of fuselage panels, you may get a clean stall break, you may get a rapid break with an unpredictable wing drop...really depends on the aircraft. An accelerated stall can produce more rapid results with unusual attitudes, etc...again, depending on the airplane, the degree coordination, etc. The buffet margins at altitude can be thought of as an accelerated stall at higher airspeeds and with less ease of recovery, and less physical feel or warning. Where the airplane may stall at 100 knots at a lower altitude, the buffet margin for slow flight may be elevated to 180 knots in cruise.
One should not think of aircraft limitations as points that can be exceeded, and any efforts when beyond those points should only be directed toward recovery. In the case of the early 20 series Lears, the "go fast" switch that many operators installed inhibited mach warnings, allowing the aircraft to be flown at much faster speeds. This was certainly possible in the 20 series airplanes; they had plenty fo thrust, and in times past, was a regular thing for many operators. It's not necessarily a wise thing. Regardless of whether a particular airplane experiences obvious effects when approaching boundaries, one shouldn't make the assumption that any buffer exists with which to pass beyond those boundaries. Nor in normal operations is there any reason to do so.
As we go faster and faster we experience a substantial drag rise, and conversely as we go slower and slower, the same occurs. There's really no reason operationally to go there in revenue operations. Whereas recovery may be possible (or may not, depending on where one has taken the aircraft), it may eat substantial altitude and presen tadditional hazards such as airframe loading or damage which are only indirectly related to the issue of airspeed or the buffet boundary itself.