A couple of ideas that i'm probably late with

A couple of things relating to token streams. I'd find it useful if there was a 'FilteredTokenStream' class - which was basically a TokenStream that you could set to ignore specified token keys.

Also, i'd find it useful to be able to 'bookmark' a stream, so i can then easily return the position of the stream to the bookmark.

Probably a bit late for those though. Sorry!