This is really cool. Did you ever consider an API to do the reverse - to insert a value at a particular point in the data?
My interest stems from this issue[0] on the Ruby issue tracker to make a symmetrical method to Hash#dig (which does something similar to, but more limited than glom) called Hash#bury. The problem in the issue was that inserting a value at a given index in an array proved difficult and unnatural in Ruby, so I was wondering if there were other solutions out there.
Another question occurs to me - does glom only support string keys?