Unless Leica brings out another Limited Edition the only BP 50 Summilux ASPH is the one that came with the Leica MP-3 Sets. Hard to find on its own and priced accordingly. Its a very beautiful lens, 'retro' style of the original Summilux, with the round clip-on hood (more effective in preventing flare, and better physical protection), and a solid brass focus mount. Of course the modern optic unit of the regular ASPH lens which as many folks say 'the best 50mm lens ever made'.
The other option you mention is the pre-ASPH BP lens. Kind of a hybrid of a new and older lens; brass mount, 'scalloped' focus ring, and older lens formula, but with more modern coatings, and a pull out hood (that doesn't lock so you need to be a bit careful in regards to the front element). Its still a very good lens and has its own 'character'.
And there is the original 50 Summilux in black paint from the 60s. Prices have gone up on these a lot in the past few years, and most of them have been well used for a look of BP with brass showing (or if very well used brass with still some BP) that can be attractive.
The 'dilemma' as you say is just a priority issue. Set your sights on what you want. A Noctilux is a different animal, an M9 is a different way to make images than film, and a Summicron in BP is another story. Good Luck with your search!