I hope we'll be seeing a set of skills to train into that extend the lifespan of elements influenced by them, or reduce the impact against repair limits, etc...
What I'd love to see with regard to element size limits on the various cores is to have it done via a capacity limit, similar to how chairs currently have a fixed amount of PVP capacity which is taken up by radars and weapons and such. Do the same thing for element limitations. Each core size has a particular element capacity, balanced such that using lots of appropriately sized elements remains possible (perhaps XS cores get unlimited XS elements and so on, or else just number tweaks until it feels right) but using larger elements will quickly consume that capacity. Like, maybe the numbers work out in a way where an XS core could technically accommodate a single Laser L, but it wouldn't then it wouldn't have any remaining capacity for other parts making it functionally pointless. In this scenario it would make sense to have a set of passive skills affecting both the core capacities and the capacity cost of various elements, so perhaps someone who put in the weeks of time necessary for a level 5 skill could squeeze that big gun in there.
This would allow clever ship builders or those with higher skill levels to produce more effective ships within the core size. Someone with more experience and a higher level would be able to shove just a little bit more onto the XS core fighter, making it more lethal than someone without those skills can produce. Or engines, or containers, you name it.
Further, this whole concept would allow for specialty cores, or even unique cores. That is, cores that you can craft with high level stuff or find out in the world that selectively ignore certain core capacity limitations. Perhaps you find a special rare gem while mining that can be used in the production process of a core that can mount engines one size larger with the same capacity cost, or cores that reduce the mass of anything attached to them, or cores with more health or more repair capacity, etc etc etc. There are more ways to iterate this than I can possible think of here. (even if you don't like my capacity idea, pleeeeease consider specialty cores separately I think they'd be super neat)
I really think this would be superior to just setting arbitrary limits based on size alone. Something like this stands only to widen ship building horizons while adding an important set of constraints to the build process. Constraints that don't feel forced upon us but are a natural outgrowth of the building system.
Whatever changes are made, the game should (in my opinion) absolutely be avoiding arbitrary rules like the ones being proposed. Certainly there will be places where they're just going to be the only realistic solution, but limiting what goes on core sizes at least can be done far more elegantly than just saying "no big thing on small thing cuz we say so."
Thanks for reading.