I agree that Penjing should be promoted and discussed more, as should saikei, sueseki, hon non bo, and even "plant art" (as per Lenz).
The idea of a separate section has come up a lot, but has not had the support yet. Instead, we just lump them all under the broad heading of "bonsai"
... with the interesting result that bonsai is now a sub-category of the broad category of "bonsai"
pootsie