Before the existence of Wild Guns: Reloaded I would have agreed with you but If that team can redraw pretty much their whole game with a team of (I believe) 3 people, including new stages, enemies, playable characters as well as some redrawn old ones to enable widescreen support, I don't think Capcom has a good excuse except stinginess or lack of expertise for not being able to draw one or two new characters as sprites as well as a new stage or two. IF they had wanted to, of course.
Yes, I'm sure it would be a significant amount of work but would it be an insurmountable amount of more work compared to all the work put into WG:R, i.e. a re-release of a cult classic game that I can't imagine had a big budget or any kind of guaranteed (mainstream) interest like SFII still has?
It seems a bit similar to Comcept and Inti Creates not being able or willing to do Mighty No. 9 with sprites because of budget reasons, multiplatform porting etc. but for them then to do things like Mighty Gunvolt at the same time using actual, decent sprites. Surely if they can to the latter, they could have done the former in sprites as well, again IF they had really wanted to.
Heck, I'm half expecting SNK to announce Garou 2 will be finished with sprites and released in 2017/18 after all their expressed interest in the title last year, which would make the request for some new SFII sprites seem even more doable imo.