Well, you have to admit that the kind of power they're getting out of a 1400cc engine is impressive and much of that's due to all that forced induction. The supercharger gives your low-end grunt while the turbo more or less provides pressure equalization from what I've seen of the VW trend with this set up.

Natural Gas set ups have different fills, so not all take that long to top the tank. The system listed in the article you linked is for the homeowner to use overnight and works on standard household gas-line pressure. Fill stations have much different equipment. From your article:
Filling stations that dispense compressed natural gas under pressure can fill a tank in three to five minutes.
We have a lot of local citrus growers that have converted many of their trucks (regular pickups) to LP and NG as it keeps the thieves at bay. They fill pretty quick, usually about 10 minutes and they've got sizeable tanks.

No doubt you can build torque with a Wankel, but this isn't what we've seen in most of the production rotaries. And at that you absolutely have to pressurize the engine. I've ran two RX-4's and have a 20B slated for use as the engine on a future homebuilt aircraft, which will be turbo-normalized.