Personally if you want a black pine get a black pine and if you're not really happy with a ponderosa as a ponderosa then let someone have it that appreciates them for their own beauty. I feel that grafting anything else on this great native tree is an abominable thing to do.
Don't let your love for this species cloud your judgement about wheter grafting JBP is a bad idea or not. It makes a lot of sense to graft JBP onto Shohin ponderosas, you get the great bark and trunk thickness of the collected tree combined with the short needles of the black pine. The large ponderosa needles tend to not work well on Shohin because they destroy the illusion of scale. Also some people don't have the time or money to grow or purchase a nice Shohin black pine. I'm not saying that grafting is what I would do, but it is a logical solution here that shouldn't be considered abominable. Grafting is done all the time in this art form.
Here is Mike's posts that relate to this thread. http://crataegus.com/2010/03/29/grafting-on-ponderosa/http://crataegus.com/2011/04/25/black-pine-grafted-ponderosa-styled/
PS- the Japanese tend to hate ponderosa foliage (not that that should entirely matter to us, but just something to note)