wrote

You'll probably see that raised to 100-150 W on HF because
there are so many ~100 W rigs in existence.

The 50W number was chosen because it's a "safe" level according to OET thinking.

If there were a 50W permit, manufacturers would quickly market a 50W rigs, just
as they manufacture 10W versions of many popular rigs for the JA market.

But "re-takeable" - if someone took the Class B test again,
they'd get another 10 years as Class B - right?

Not in my proposal.

1) What test would be required for upgrade to Class A
for current licenses?

Pass the Class A test.

2) Would there be any experience requirement for Class B
hams that wanted to upgrade to Class A?

I originally proposed a "time in grade" requirement, but in retrospect I can't
find a logical regulatory reason to defend the idea.

3) If the licenses are issued "for life", how would FCC know when
an amateur expired unless next-of-kin sent official notification?

Since no benefits accrue to an "expired" ham, the FCC has no interest in their
passing.

4) What would happen to the vanity callsign program under your plan?
Obviously a Class A could get a callsign from any block, but what would
be available to Class B?

Each new licensee would get a new call in sequential order. Vanity calls would
be available to any licensee without regard to "blocks".

73, de Hans, K0HB