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.
"As long as they give a good talk" - you're not talking about one specific person but in fact a general population of speakers.