Thanks for the reply, I already have insurance with the Sate Farm/OTFR deal as you mentioned and yes it's cheap !, cost me 300$/yr for five bikes.
As for the green plate (without previous ownership), I also found how to proceed, if anybody as the same issue, there is pretty much 2 options :
Option #1
You get all the bills of sale since the bike was new (including the one you get from the seller), and since you can prove "continuity of ownership", the MTO will issue a ownership and green plate. If you have NVIS form with that, it help a lot too.
Options #2
If you dont have all the bills of sale, you make a certified affidavit stating why you are missing that information, what information you have and that to the best of your knowledge this information is true and that you are the legitimate owner of the vehicle. Some MTO have a commissioner on site, so you can bring your affidavit and they make you swear and do all the other formality to have it certified. Then you proceed to the registration to get ownership and plates.
In both case you do not need any insurance to get ownership or plate. (but yes, I know you need it for public land!).
Like Tom said, some offices will even do it if you missing some of the papers, especially in smaller towns, but thats kind of a hit and miss... if you have the time to try
Hope this would help anybody like me thinking about buying used bike that was not previously registered. I went trough the process recently and it wasn't as hard as it looked.
Simon