Better to just avoid it by keeping incentives aligned with winning your qualifying heat.
https://www.youtube.com/watch?v=kQNY5htc9_k
When the US 4x100m swim relay beat France about three olympics ago (the one where Phelps won all those medals), France was comprehensively faster man-for-man aside from Phelps in that relay.
The US won because Jason Lezak, the anchor, swam in the wake of the final French swimmer (a draft basically) and was able to save energy and pass him.
If the US and French had been separated by a lane, the US would have lost.
If you are slightly faster (and especially if you go out faster) than your #2 rival, you want to have a lap between you to deny them the draft.
The entire point of qualifiers in most sports is to reward better participants - otherwise they would have incentive to sandbag their performance or perform other shenanigans for preferential matchups.
Why do you believe this should be the case? Keep in mind the majority opinion of most forms of racing and other competitions is to reward competitors for their qualifying or heat performances by assigning the most valuable starting positions to the top qualifiers. This is generally considered more fair than randomizing the final’s lane assignment (or grid order, etc) because it reduces the chance of BS in the finals itself and avoids perverse incentives in the qualification rounds.
My reservation with swimming is that if you were randomly assigned to a middle or side lane in the qualification stages, your advantage or disadvantage is compounded as the competition proceeds. It's not clear to me how lane assignments are conducted for heats; perhaps they use a seeding system.
https://www.nbcolympics.com/news/swimming-101-olympic-compet...
If you wanted a fair system, there would be no qualifiers and no simultaneous racing. You would just have everyone compete at home and mail in times whenever they have a new record. Like eg speedrunning for computer games is done today, or like any world records for fastest time are done.
Track conditions can change throughout qualifying so that the later qualifiers might have a slightly faster or slower track.