Not many people - Including this evil monarch butterfly here - are happy with the current player level protection and you need to listen to your community Wiz and change how it works.
Here's two examples I've seen today on different ends of the AEverse, where people voice their displeasement..
I think the level protection system is broken as is, you can stay at level 29.99 and remain untouchable. My personal opinion is that level protection needs to be based on a percentage of your current level. Something like you can only attack people half your level and higher and up to twice your level.
IE: you’re level 100, you can attack and be attacked by level 50.01 to 199.99(sic)
fixing level protection and giving it a time limit until it expires should be the biggest and most needed change.
after that... hmm, maybe fix up fleet tax system for 2.0?
thirdly refund for when commanders die/dismissed? (a simple 50% XP rebate would be fine)
but yea, bases being destroyed is a huge no.
and sorry to say but I think you're in the minority for guild size nerfing. (though I'm inclined to agree with it I'm 99% sure it'll never happen.(sic)
.. If you changed how the level protection works, maybe your new server Mystic, might be a little more mystical than you think.