For plural? Yeah, easy peasy
For singular? Close to impossible without sounding like a monster.
And I don't mean monster as in the recent "woke idiocy" type of way; I mean monster as in the "de-humanize a person and treat them as an object" type of way.
Right, so to extend the everyday scenario a little further for clarity:
"Apparently they're sending someone over from head office." (plural)
"Do we know who?"
"No, but can you pick them up from the station? They're arriving at three o'clock." (singular)
This is hardly an unusual situation; it's easy to imagine countless variations...
There is no way in hell you can argue in good faith that using masculine/feminine pronouns in ignorance is anything
but "monstrous" or de-humanising, especially in situations where you have no information to work from. I would argue that the assumption in that context is quite obviously more de-humanising, as you've made a judgement of contextual "worthiness" of the human being you're speaking about.
I've been seeing this "argument" around lately, I can't help but assume a lot of it is stemming from disgusting politically-motivated moral panic revisionism. Singular "they" in English is literally older than the current usage of singular "you". Absolute madness.