Which is NOT the case in your current proposal.
From your starting point:
This also affects DEFENCE fleets!
If you get a FR incoming and defend against it with FI and if you PL that defence fleet 1 tick - which is usually the case! - then you will
not be able to use that fleet immediately when the attacker recals at eta 7.
The defence will be stuck with a 1 tick return time.
And more important: this round there are
already 4 alliances which live launch 40+% of their attack fleet between 01:00 and 06:00 !
So even without PL you would
still have had at least 40% of the fleets. And possibly more.. since those that are now on PL+1 would likely just live launch.. or land tick set one tick earlier..
These attack fleets will require you to wake up defenders - defenders which in turn can then also live launch their attack fleets.
The problem you want to solve: incomings during the night.
Your propsed solution: rework prelaunch. In the
very best case that would have reduced nightly incomings this round to 40% of what they were.
And even that is stretching it.. For the fleets that PL+1 the extra 1 tick return time hardly matters after TT4 finished..
(And before TT4 it would just be a live launch because of the slower travel)
If you really want to lower nighty incs then the suggestions from Paisley make a bit more sense..
For example: higher XP gain for fleets launched during the day
could make sense from a game point of view.. Landing an attack during the day requires more experience after all since it is easier to get covered - since people are awake..