I think some clarification might be in order, here.Sorry, I don't have any magic for you on single rotors Wankels. They would be pretty heavy for the power produced. Several reasons:
Really big counterweights are necessary;
Firing order vibration would be huge, requiring one or both of, torsional pendulums and very long stroke "soft" isolation system.
With only one rotor, the entire eccentric mass of the shaft and rotor has to be balanced with counter weights. With two or more rotors, the primary (up and down) imbalance is taken care of by having the eccentrics evenly distributed, and the counterweights only have to balance the pitching moments. The more rotors, the smaller this whole effect is and less counterweight size needed.
The firing frequency on a single rotor is one per rev and really strong. Torsional pendulums would be useful, but they would have to be really big to tame that low a firing order. A soft system would require pretty low spring rates, which means a lot of travel and volume occupied by the spring system. You might need both...
In the end, Wankel single rotor engines will be heavier and more complex than two rotor engines of the same power.
My airplane, a Q200, originally had a single-rotor Wankel that weighed, firewall-forward, right at 200 lbs with a Ross PSRU and aluminum end housings, wet, with a wooden prop. The builder wrote extensively about this airplane in Kitplanes during its development and did a nice job on all of it, though not without a learning curve. He put the output, naturally-aspirated, at around 130 HP. He has stated to me that he plans to use another Mazda engine in his next airplane, which will be his seventh build, having been very impressed with the end results on airplane number six.
Unfortunately, someone else made an offer on the engine/PSRU separately and he sold it a few hours before I contacted him about the plane. I'd like to duplicate the previous engine in rough numbers, with an aluminum single-rotor and a similar PSRU.
Single-rotor 13Bs don't have as good a HP:weight ratio as dual-rotors, but they're still very good, and excellent for aviation. Using aluminum end housings saves a lot of weight, as well, but they're expensive at around $2000 each.