I would support any manufacturer from any country making rangefinder lenses, as long as they are of adequate quality and performance. The Mandler lens looks nice, and I hope that it works out for the company and the users.
This may be an unpopular opinion, but I have never understood the hype around the V4 Summicron. I used one for years before it was stolen and never thought to replace it. It has the typical focus shift of all of the pre-ASPH 35mm Summicrons, "king of bokeh" is a pretty ridiculous moniker for it, and it is insanely overpriced today. Instead of replacing the stolen V4, I opted for a NIB 35mm f/2 UC Konica Hexanon, which has similar ergonomics, size, performance (even with its own focus shift), and was about half the price of a used V4 at the time -- and I have never looked back. Today, there are so many 35mm rangefinder lenses that outperform the V4 and still have "character" or whatever.