I assume Luecke's script

In reply to MM Typeface and [FATAL] GPOS feature 'kern' causes overflow of offset to a subtable:

I assume Luecke's script doesn't circumvent all such limits?

I'm not sure what you mean. It circumvents the kern subtable overflow limit, which is what it is designed to do. I've used it -- via the VOLT export option -- on some very large fonts with the class+exception equivalent of >100,000 flat kern pairs.