I would guess that it wouldn't be worth the hassle of the inevitable inaccurate identifications. The most ergonomic password entry tool I've used is rofi-pass [1]. It's so effortless that I don't think anything smarter could improve on it in practice. It works in a predictable and way in any application (eg SSH pw in a terminal) without any complex integrations being needed and once you get used to using the hotkey it's basically as quick as form autofilling.

[1] https://github.com/carnager/rofi-pass

Hmm unfortunately I don't have an answer for your question. Though sounds like KeePass is the next best thing. You can define custom auto-type patterns, for forms that don't follow the typical <username><tab><password><enter> format. It's great for saving ftp sites for filezilla, or ssh logins.