Add rate of fire to your criteria. When you say "nor could it have competed", do mean they were not capable or not allowed? Pneus do take a lot of effort to run in the teens, but for RT's that's cruising altitude.
There was some discussion about GoG trying to use a double trigger on the enmy. The vibe and enmy rate of fire goes along with the "soft" bolt stroke and low pressure. They are strangely unlike an ion, in that there is not a lot you can do to them practically as modifications.
The nice part about electronics is that you can use the same marker as the players and insurance companies change their minds. Sometimes they want a hard rate limit, or you can't play with that particular marker. If I tune a mechanical marker to be capable of 14 bps, I may be out of luck even though it doesn't have an LPR. On the other hand, you can build 10,000 electronic boards, connect them to off-the-shelf solenoids for pretty cheap, and still be confident that you can cap the ROF where you want. Can you imagine the mess if you wanted to ship 10,000 Tippmann F/As?
My RTs liked 15 bps pretty well. As it is, I have to be careful with my RT setups to stay below 13 bps. At least the chronographs are pretty good with rate measurements.