I do a few just like this and WFP the lot and they come up very well indeed, you can do them with a very light touch with WFP, not a problem at all.
Quite right about the stone sides though, get them wet and it's sand all over the glass!
Some will leak, but I just tell the customers this and so far have never had a problem, it's only usually a few runs at best.
Real old leaded is hard to do trad, the cloth's/scrims catch on the lead and other bits all the time and I would think you will end out putting more pressure on the windows doing them trad than you will doing them WFP, well, providing you have a light pole and brush that is!
Ian