Hi Glider,
The Mosquito building rules and restrictions state that there must be a boom and it must be straight. (section 12)
I have provided a link to the rules below:
Mosquito Building Rules and Restrictions Section 14.4.1 also states that the mainsail shall be attached to the boom at the tack and clew.
So I guess that if you try a boomless setup it just won't be a Mozzie anymore.
The only good thing is that the mainsail leech and quarter leech distances only have maximum dimensions so you could shorten it to whatever you wanted. Power and performance would be compromised and you would potentially be shifting the centre of effort significantly forward.
Good luck with your projects.
Regards,
Peter