Gero,
The mast tip rule was introduced to minimise the perceived performance difference between carbon and aluminium masts.
Removal or even further reduction of the weight means you are affectively forcing the class to be compelled to use the more expensive carbon masts. If you think I'm wrong, ask yourself how many top A classes are sailing around with aluminium masts.

As far as adjustable T foils.
I designed some adjustable T foils a year or so back and the cost difference is not significant. Closer to 300 rather than 3000.
You can retrofit a system to existing foils. No big deal.

Regards,
Phill