Not particularly difficult, the issue is more that they're long. It's a lot of work for a fan translator, especially since a lot of that length comes from sex scenes which are somewhat boring and annoying to translate. It would probably take a group to divide the work and make it more manageable but this kind of nukige just doesn't have the kind of dedicated fan following to organize something like that other more story-driven VN have.
That's why I doubt there will be another fan effort to translate a Bishop game. And it seems there's no interest in bringing them overseas officially, so we're stuck with MTL.
As for new games, like I said a new one is coming out at the end of the month. Kyousei Shihai it's called.
Forgive me for the self-promotion, but I've made
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on my blog covering it since its announcement, in case you want some English-language information about it.
The most recent game before that was last year's Shinshoku, and its
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indicates there is a MTL patch for it already (from sugoi, as expected).