I get the theory now (although like you I'd be worried about damaging anything else in there with the soldering iron)... but the bulbs are an issue as it needs a small H6W bulb and getting an amber flashing one of those is alot harder.
I'll only try this when I know there is a steady source of amber flashing bulbs I think.
Ive been using the ones i got for at least 6 months now, and theyre great. I have 2 complete sets (2 front and 2 back) bulbs for sale. I can get more but would have to order them from the manufacturer. its not a problem. its just that i only know of the MK5 that uses these bulbs. All other cars ive had use standard indicator bulbs.
the benefit of these bulbs is that they have canbus built right in, and you dont have to mess about with resistors, which could potentially melt your light units which they did to my old audi a4! thats why i went to the trouble of sourcing these ones.