Never had this come up before.
Is it allowed to delay the start of a game in a FIDE rated section if both players agree. One player has asked if this is allowed and is concerned with arriving late (after forfeit time) for the first round.
My instinct says no, because the opponent cannot be asked until the pairings are published. A 1/2 point bye is what I suggest for this situation. The concerned player is a titled player and likely either the #1 or #2 seed in the field for the event.
I mean, I wouldn’t agree to that because starting late can mean ending late.
…I can imagine adding that in as a variable default time in the regulations of the event, which would get you into the standard Laws of Chess 6.7 and looks legit, but again I wouldn’t agree to it.
Care has to be taken to prevent any player from receiving special privileges contrary to the regulations posted for the event.
Allowing players to start a game later may convey to them additional information about results of games that started/ended earlier, which may be more useful the later in the tournament it is.
In a norm tournament, the expectation is that all games are played on an equal footing with the same conditions, e.g. at the same time, with the same time controls, at the same location, etc.
However, in your particular situation relating to a round 1 game and assuming it is a non-norm event, if the opponent agrees with it and the tournament isn’t adversely affected by the potential of this game ending much later than others, it certainly is something the Chief Arbiter would be entitled to allow.