That Scarbee VKFX package sounds really good. It has a Fender Twin emu w/ spring reverb, mod fx based on the Univibe, CE-1, Bi-Phase, Wah, TubeScreamer, tape echo, and more. I like using it as a send with just the tape echo and maybe the amp sim or a env. filter working for some dub flavor. Dunno how authentic the Mu-Tron is, but the filters and phaser sound great to me, but still somehow sound too thin when used heavily.
A good Leslie would be nice...I am waiting for my reg codes for the Creamware B2003 which supposedly has a nice one (better than the NI B4). The thing is that the room & mics have a lot to do with how these sound recorded too. Doesn't the new NI B4fx allow you to choose different cabinets and mics now?
I am really confused about the lack of good gates though! Sonalksis announced one that I think most people were excited about, but they have had nothing to show for it over the past year. I really only use gates on drum close-mics or triggered for effects but somebody needs to put out a nice smooth one with multiple smooth attack/release curves!
I think Hydratone does the 550B well, better than URS. Nobody has tried making a 550A right? Never used that one but heard many times that it is sweeter than the B (of course this is a very subjective matter!).
I can think of a few more vintage effects I would love to see:
1.) Hopefully UA will do their 175/176 vari-mu limiter to add to the compression pallete (no we do not have enough yet!).
2.) An old dbx 160 x (or vu, xt, one of the early half-rack ones) would be cool for kick drums or bass guitar, and who knows what else.
3.) Analog distortion modeller...something that would let you dial in the effects of different big fat input/output transformers (harmonics, spectrum changes), let you overdrive nice sounding modelled FETs/MOSFETs/BJTs/etc or op-amps, and incorporating some kind of soft-clipper or good sounding 0-attack peak compressor (like tape

) to soften up and round transients. I would use something like this on every channel, probably only reaching for whatever pending tape-emu there is for submixes or the master buss.
PS - building an actual Wah circuit is very simple, and cheap (not to mention fun)! It is worth investigating...how often do you need more than one wah per track?