Hello Aub!
Why not, just keep it all Z centric, do like all other single model clubs do, agree to meet at a central location that suits all ( watch for the arguments on that one!) just gather at a local park, lift bonnets, go Ooh Aahh a lot, than have a dinner, tjen go for a drive on some nice country roads, not too rough though, dont want paint chips on the trailer queens.
Forget any competition, sprints lapdash, hillclimb, etc etc, as that is consideted too risky to a clubs finances, nowadays!
As low event entrant (Z cars only) numbers will make the risk of track hire anywhere, to cost prohibitive, and, lack of CAMS officials within a club, along with the manpowere required to run events, will negate it.
A loose AASA run event, tacked on the back of a pre-existing AASA organised event, could satisfy the mine's fastwr than your's brigade.
There is no reason at all that a Z only Nationals could be run, at any time, considering the plethora of Jap based car shows/events etc tjat are held all over the country these days.