Your analysis is spot on. The apex seal problem is a materials problem and is a difficult but not impossible nut to crack. Given the appropriate materials it should be possible to run a Wankel with out oil injection to lube the seals. Hydraulic vane pumps running fireproof water based fluids have similar problems with vane tips being highly loaded and running at very high surface speeds. These problems have been solved with proper metallurgy and/or ceramics. I have confidence that the apex seal problem could be solved.
The chamber geometry problem is inherent in the design and there is nothing that can be done about it. Unlike the piston engine where a variety of chamber designs are possible. Hemi, pent-roof, squish all reflect varying degrees of exposed flame area and thereby are optimal for differing engine parameters. A hemi allows the largest valving area possible, giving better breathing (low end torque) at the expense of quench area (combustion inefficiency). The squish compromises breathing but gives the lowest quench area and highly efficient combustion. A pent-roof is a middle of the road design that works well with multiple intake and exhaust valves at the expense of mechanical complication. A design engineer must weigh all of these considerations when striving for a balanced design. Unfortunately, the Wankel principle does not allow this latitude in tinkering with parameters.
Considering engines in the abstract, almost anything that causes air to move can be made into an engine. A fan can become a turbine engine by adding a second fan and a heat source (turbines have been built that run on powdered coal!). A positive displacement pump of any sort can be made into an engine by mixing fuel into its working fluid and igniting it at the proper point. That being said, consider the piston engine as we know it. Cylinders are easy to machine, arbitrary cam like surfaces are not. Cylinders can make a piston bore and a piston with liberal tolerance allowed and still be sealed with a simple cast iron ring. Crank mechanisms are essentially a bunch of cylindrical surfaces connected by as-cast metal. Insert bearings with forced lubrication are easy and robust, forgiving of large tolerances. Needle, roller, or ball anti-friction bearings are also forgiving of lubrication requirements, but inherently more complicated, bulkier, have finicky tolerances, and are expensive (& noisy!). Poppet valve technology works in everything from lawnmowers to F1 racing at ridiculously high rpm. The rotary valve (Coates engine) is a complex solution looking for a problem that doesn't exist (looks neat though!).
My point is engines are fun! They are fun to dream up, they are fun to build. You might even be able to get somebody to finance your dream engine and go for production. But the Otto cycle piston engine has been in continuous production for over one hundred years. It has been subject to a process of continuing development by market pressure, optimizing virtually every aspect of it's function. We have pushed the laws of thermodynamics and economics about as far as they will go. Todays engines represent the pinnacle of sophisticated simplicity, balancing manufacturing cost, performance, and efficiency. It is not an easy task to replace it. Adding cost and complexity will not suffice, a break with the past is needed not a different way to do the same thing (fuel cell?? maybe).
So endith today's lecture.
Regards,
GtG
PS If it don't go, chrome it!
Ah, thanks for the flashbacks to ICE 101 and 102 I took back in college. I learned more about engines in those two semesters than probably 99% of "car guys" know today.