wouldn't foils on the daggerboard just raise the board up in the daggerboard slot?
What would be tougher would be handling the heeling moment while up on plane. The Sunfish has no accomodation for hiking, and hiking gear would be rather difficult to install due to the lateen rig.
you are right... we often sail fully hiked out on many boats. But when we do, the righting moment of our weight is aided by the boyancy of the hull on the leeward side. When up on foils, you won't have this part of the righting equation.
When I say "accomodation for hiking" I mean anything other than a simple hiking strap, like a trapeeze or wings. If (when, maybe) I'm experimenting with trim / balance while up on foils, I think I'd rather be perched on a windward wing, rather than having my backside cantilevered out over the water. It seems like it would be easier to manage.
Sailcrafti's comment above is interesting, and worthy of consideration. The V shaped foils that rise above the water on either side have a decided advantage in the stability factor. They provide a means of regulating ride height above the water with having to use a mechanical mechanism, plus the built in dihedral automaitcally wants to resist heel.
Remember the centerline, dual foil arrangement like on the Moth are used because the rules prohibit the V foil design. They felt that it might constitute a form of dynamic multi-hull, and banned it. BUT since we aren't bound by any rules, the design should probably be considered and discussed.