David Megginson wrote
I understand that it's a fairly cheap modification (as simple as a little
valve under the front of the panel).

If you own an experimental, what you say is correct.

If you own a certified airplane, you may rest assured that the weight
of the paperwork will exceed the weight of the installed components.
A change to the pitot-static system is considered a major alteration.
If it's a manufacturer's kit or STC, it will be expensive. If there
is no STC or manufacturer's kit, it will be VERY expensive or
downright impossible because it will require a field approval, which
these days usually requires you to hire a DER/DAR.

Just one more way the FAA keeps us all safe from unproven technology.

Michael