How can i print white ink on transfers with a p600 without dtg conversion

Goodday Everybody,

I have been a long time reader and previously registered member but lost my account, so i created a new one.
I have been in the business of transfer and decal printing(and selling) for about 5 years now operating from the Netherlands.
Lately i have a some requests for white printing on clear transfers (especially decals), so i am exploring my options.
As my business isn't that big i don't feel like buying a 15k Solvent printer to print spot color white, and i don't like the downsides of the oki printers (white on top only and losing black).
Few months back i tried the ghost white toner option, but i just can't get the 2 prints to match close enough to do 2 pass printing even when i throw in my fully adjustable HP enterprise M553 i can get it to print at the right spot but further down the transfer it offsets (heat shrinkage?).

When exploring the internet i found a lot of post of memebers here using a Epson Surecolor p600 for a full DTG printer conversion, and i think a part of this is what i might need.
I have a Surecolor p600 i could convert, also have a stylus pro 9600 and a stylus pro 6000 which i don't mind repurposing, even have a ricoh sg3110dn which was previously setup as sublimation printer but don't use it anymore.

So my questions to you...
Is it possible to convert a Epson p600 to print white ink without complete dtg conversion?
If so is it just new cartridges, cleaning the lines plus installing a rip software?
Where can one get regular pigment white ink to convert the printer with (preferably EU based)?
Any recommendation in books or sites to read up on this topic?

Any help will be greatly appreciated.
Even if your opinion is of this being a bad idea, i like to be warned before hand.

Thanks
Anton