Thank you for all the replies
Keeping in mind this regulator should be easy and cheap, the solution of buying one from the states isn't easy and cheap for me, so i kept studying the subject and i found something interesting...
The system with field coil isnt that forgotten since 1977, seems many automotive generators still use this system and so they have the same regulation and rectifier system
But i suddenly came to a stop on this directidirection when my curiosity took me on the workshop manual of my 2005 kawasaki zrx1200
Guess what. Its generator has the field coil system and separate regulator and rectifier
Prices of genuine reg and rec are crazy about 399 each
But i found an argentinian company which makes those regulator easy and simple for few bucks, they sell parts also in italy so i could buy one regulator from an italian seller on ebay for 25euros which is about 30dollars i guess, no customs, no forever waiting...
I will give it a try and get back to you if you're curious too
probably i will fry the whole motorbike but well this is the risk we all take for experiments and improvements isn't it?