The A Class cats at 18 ft Length with 7.5 beam seem to foil well.

Sail area to length ratios are a key componant .150 sq ft on an A is proportionately easier to stabalize as is 300 on a 25 ft 14 ft beam C Class cat --20s would be somewhere in between with similar performance and 2 crew --but more practical and affordable than a C Class cat .

Given how many enjoyed the Trifoiler The Rave foiler and others it would seem foilers take no unusual skill.

20s were historically the B Class cat --The Tornado design dominated that category for decades
You are correct --a few need to build foiling 20s then build a racing class around it--the CF 20s with radius boards are close already --they need board mods to the L foiling shape and rudder redesign.They aren't far off now and surface foil.

Given the foiling mode being predominant for speed I think hull design -rig design -and foils themselves will continue to be refined to complement foiling speeds --Hulls no longer need to go THROUGH the water but should sit on top moreso --Bows in particular need to resist nose dives as they fall off foiling mode . The sail plan itself should be more oriented to help provide verticle lift --.

Funny -how basic human behaviors have not really changed much over time --there will always, ALWAYS be a portion that say in essence ---hey --we have perfectly good sticks to drag along the ground with mastadon skins stretched across to carry food --why would we need that round wheely thing attached to it ?

have fun
enjoyed the hypotheticals Sam
best regards
Carl