It's really cool to hear about another GiST improvement proposal. I'd like to connect recently committed GiST ordered build discussion here [1] and further improvement proposed [2]
I've tested feature [1] and got 2.5-3 times speed improvement which is much better I believe. There is an ongoing activity [2] to build support for different data types for GiST. Maybe you will consider it interesting to join.
BTW you may have heard about Gin and Rum [3] indexes which suit text search much, much better (and faster) than GiST. The idea to process data in bigger chunks is good. Still optimize index structure, minimizing disc pages access, etc. seems better in many cases.