How about a list of known/up-and-coming/regional engines?
I know of 2 members here that have written their own. Not sure of jmmcormac's URL though :)
Member glacai [webmasterworld.com] wrote Mojeek [mojeek.com]... written in C from scratch as it says on there.
Alongside DuckDuckGo, both use privacy as a major selling point.
Majestic, ahrefs and other backlink providers are international search engines of sorts... perhaps with the addition of storing text into searchable indexes they could get on board?
For anyone considering the task CommonCrawl [commoncrawl.org] has a good sized dataset to work with.