Original was: "problems a speaker at a conference might have, as long as he gives a good talk/presentation."
The pronoun refers to "speaker", singular, yet indefinite, we don't necessarily know who it is.
Let's substitute "they: "problems a speaker at a conference might have, as long as they give a good talk/presentation."
Yep, works for me, but I think the "they" definitely talks about about that single (if indefinite) speaker. Yet we use the plural of the verb ("give"), so the sentence is confused, grammatically. I wonder what will give as this evolves, whether "they gives" becomes acceptable or we simple leave "they" grammatically plural even when it is semantically singular.
Language. Fun times!
"As long as they give a good talk" - you're not talking about one specific person but in fact a general population of speakers.