Brilliant! This change would make Specialists desirable, but incredibly far from mandatory. It would also be nice if Specialists had a bonus to forbidden melding - +10% meld success rate would be enough to make it worthwhile.
I'd also like it if Specialists had a flat boost to Craftsmanship and Control ratings for their recipes - say +25 or +50 apiece. That way, Specialists would have an easier time making the items in their crafting log, but the difference could be overcome with better gear/food/potions/FC actions/etc. Such a system would need to be tuned so that the highest rated items can eventually be crafted by everyone, but Specialists would have an easier time of it.
I will say that I think there are some recipes that should be locked to Specialists, but that they should be cosmetic only (housing items come to mind). That way Specialists still have something that is just for them to be able to make, but it's not something that would have any impact on the PvE game.
That's easy: give ARM (and LTW and WVR) the ability to create green 195/200 DoW/DoM armor that has sockets--and specialists get an extra free meld.
EDIT: All of these changes would assume that most recipes that are currently specialist-only are made available to all crafters, regardless of whether they have the right Soulstone equipped. It doesn't even make sense from a lore perspective - you are basically given a blank Soulstone, so these recipes are yours - you wouldn't suddenly forget how to make the things you've made just because you don't have the Soulstone that's been learning from you and only you. I can see it making repeated recipes easier (the more you make of a thing, the easier it is to make that thing), but not sucking the knowledge and technique required for certain recipes out of your mind when you don't have it in your Soulstone Pocket.