With thin stuff like LavaCore/Sharkskinz/Exowear/etc, I would not use luggage space to carry short stuff if I was going to take long stuff anyway. I can't imagine ever being too warm in the long stuff. And that would be the only reason to take the short stuff.
When I travel, I take all my own gear, including a bunch of bulky camera gear. Luggage space is at a premium. I try to take one suit that is the warmest thing I'll need. If a LavaCore - or even a 3mm - is actually TOO warm, then I can go in board shorts and a rash guard. If it's too warm for a 3mm, then that means it is hot bathwater and board shorts alone would be plenty.
For a week in TCI in August, I took an Exowear fullsuit and some board shorts and rash guards. The Exowear was warm enough but definitely never too warm. The water was 83-84F. I could probably have dived just shorts the whole week, but the Exowear gave me the full coverage protection I wanted, so I wore it for protection, not warmth.
When I started diving, I bough a 3/2 wetsuit and a bunch of Lavacore stuff. My thought was having all that versatility by being able to layer. It never really worked out that way. Now, I could be perfectly fine to just and only have something like the Exowear full suit, a 5mm full suit, and a drysuit. If it's too cold for the 5mm, then I go dry. If it's too warm for the 5mm, I go Exowear or just shorts. Totally works (for me).
It IS possible to really overthink this....