Steve, I'm glad to hear that lexical scope is indeed achievable,
although I'm dismayed to find it's rather clumsy.
About macrology, a LET-like macro which guaranteed lexical
binding seems useful.
The stuff about programming conventions is beside the point;
either the programming language guarantees lexical binding
or it doesn't. You will recall we arrived here because
reasonable people made different assumptions about symbol LB.
I'm in favor of implementing lexical scope in Maxima,
although there's no need to replicate CL's craziness.
I suspect most user programs would work the same if function and block variables
obeyed lexical binding, so, while it would be a substantial change,
the trouble it causes for users would be tractable; no need to dismiss
lexical binding out of hand.
best
Robert Dodier