Huh, didn't know abbrev had that limitation (wonder why?). Gave it a go in espanso (https://espanso.org/), and it does work there.
Edit: it would need context awareness too, which somewhat rules out espanso, otherwise space indentation will be difficult. abbrevs at least can be defined per mode, but ideally it would be based off the face (so it could work in comments or strings).
You could bind it to a Compose key sequence, e.g. "Compose+Space Space". (Analogous to em-dash, which is "Compose-Hyphen Hyphen".)
But it's still an extra keystroke. And I worry that I'd cause problems editing non-UTF-8 documents if I retrained my fingers to use it at the end of every sentence and then didn't remember to switch back to the ASCII way of doing things.
