The illustrious LHF has commented above that this is not possible out of the box, and requires editing the innards of Lua, starting with http://www.lua.org/source/5.2/lvm.c.html#luaV_tonumber
Marking this as the answer in order to close this question. If anyone later chooses to provide an answer with in-depth details on what needs to be done, I will gladly switch the acceptance mark to that answer.