Hmmm… I think this is something that @Marc_Keyman and the Keyman team should weigh in on. On most predictive text keyboards that I’ve seen, if you start typing with a capital letter, then the keyboard will propose words from its word list that it has itself capitalized; I’m pretty sure that those capitalized words aren’t in the word list, but that the keyboard produced them on the fly. So if I’m starting a sentence, “Howe…” it will suggest “However”, not “however”. If the keyboard only offers the lowercase and I tap on it, I would need to go back and capitalize the word later (if I want to obey capitalization rules…). I think the Keyman predictive text keyboards currently don’t produce capitals from lowercase words, but I think they should, and it seems to me like maybe that should be a fairly high priority for the team.
My take is that all lowercase words in the word list should be allowed to be capitalized by the keyboard, but that anything that is capitalized in the list should only be allowed to be uppercase - which would serve to maintain proper names. (And of course, if you start typing something in lowercase, but it is only capitalized in the word list, that should also be proposed. E.g. typeing “keym…” should propose “Keyman”.)
If we keep capitalized words as is from the texts you analyze (what you seem to be suggesting), then certain words would be capitalized in the list, depending on the texts you analyze, but others wouldn’t. Again taking the example of this post, the word list would have “Again”, “If”, “My”, “So”… a pretty limited inventory. So I think the predictive keyboard needs to be able to produce an uppercase version of any word in the word list, but not a lowercase version of any capitalized word in the word list.