Stone, since budget is a big problem for you, you'd do well to settle for the good enough, viz., ShenHao/DaYi. The two are identical as in come out of the same machine shop and differ only in their badges, both get good reviews, and good enough means good enough. Don't loose sight of your goal, which is, I think, to shoot 6x12 on roll film, and isn't, I think, to have spiffy gear.
About the Widepan 6x12 roll holder, I didn't mention it because it seems to be out of production and used ones are scarce. To my eye, never having touched one, it looks like a good imitation or simply a rebadged Horseman.
Re w/a lenses, I have a 47/5.6 SA that just barely or almost covers 6x12. On 2x3 it doesn't need a center filter, on 6x12 it does. More expense. If one is your heart's desire, it is one more reason not to splurge on an expensive back.
Re your heart's desire, reconsider. The widest lens that covers 6x12 is -- I could be mistaken -- the 35/4.5 Apo Grandagon. It needs a center filter too. Very expensive lens, expensive center filter. It sees the same horizontal angle of view on 56x112 as an 11 mm lens sees on 24x36. Continue dreaming and saving your small monetary units.
Re short lenses, what's your 4x5 camera? Not all will focus really short lenses. More expense looms ...