I'm using the "multisite language switcher" right now, seems to do the job but it's acting a bit strange in my setup, hope the developer can help me there.
you are right, the payment with all these currency converters is the fixed one configured in the shop. as i need only euros and dollars the wp multisite setup (ger & eng) seems to be the right decision for this.
i found one small quirk with jigoshop & suffusion commerce pack: if you define grouped products, there will be additional the (untranslated) word "From:" (for the lowest price of all the grouped product) so the price doesn't fit into the ribbon, so we have 2 "bugs"
untranslated phrase "From" (or is this from jigoshop?)
ribbon to small for phrase & price
yeah, haveing two seperate shops involve a lot more work, for the next shop i will use the import function for shure, adding all the products twice is really a pain in the *ss