Its difficult to get a good system going that everyone would like, and maybe there is one that is entirely different and seems promising from the one we have right now, but it will take a long time to make it, and there's always a risk that it might not work at all in the end. So lets try to improve on something we already have.
Right now sieging only works on the abandoned cities or newbies. The shield system can be abused in various ways, here is a list that I can think of from the top of my head:
* you can build multiple village claims to surround your main village, have walls on each layer, and make as many layers as terrain allows you to;
* you can have multiple villages placed next to each other and move everything from one village to the other during the raid;
* you can surround only your walls with the village claim and have a whole bunch of personal claims on the inside of the walls not overlapping with the village claim, that way raiding each plot separately would take forever.
The first two points could be solved, or at least make it harder to exploit by increasing the minimum distance between the villages from 3 tiles, to 30, or 50, or even 100, whichever works, i personally think even 100 would be fine.
The third point can be solved by reducing personal max shield value, so that it would be possible to siege personal claims in 1-2 hours. if people want a better protection they should make or move to a village its really not that expensive or difficult. Otherwise personal claims should only be a good defense mechanism for the early game or against weaker players, and continue to serve later in the game to prevent crimes on your property and to have a personal rule set on that land.
Another problem with sieging that I see is that it takes a lot of risk and rarely gives any reward. If you are raiding weaker players, they usually have lower quality things and hide all of their carry on baggage with valuables on their offline characters anyway. If you are raiding a village that is as strong as yours, there's a high chance you will get ambushed during the raid when you are physically drained by the long wait and boring siege and expect any retaliation the least... which is totally fine, but its one of the reasons people rarely raid someone their own size, its great risk and very low reward (no reward at the moment because of shield abuse).
I can't really think of a good solution for it, but it would be nice now that we have a kingdom system, to have raiding another kingdom give you kingdom points or xp, or even both. If you belong to a kingdom and you raid another kingdom's domain you get points by damaging the shields, and you get points / xp by killing another kingdom's players depending on how developed the character was. To have some sort of reward even if by the time you break the shields and everything's been hidden, it is still better than nothing.
Also it would probably be better if you didn't have to kill and destroy everyone and everything, but instead if your kingdom could annex villages (village claims) for a certain amount of time (week or 2) and get xp out of it for each authority gain of players, even without expanding your kingdom claim over it, and after the week (or 2) have passed, you would have to send in your kingdom representative back to that village idol to reset the timer. If a village decides to call someone else for help and/or make an ambush they can do that, or they can submit. Probably would be a good idea to have some sort of reason for annexed village to revolt, maybe have some sort of a debuff on the annexed village players.
That's all I can think of for now, I haven't really gave it much of a though, just had an idea and wanted to share, feel free to add to it, comment and criticize. The issues listed here are a few of the main reasons why many people I know have stopped playing, there was no reason in growing qualities when you couldn't do anything with them at the end. Other reason was lack of late game content.
P.S. I think removing cap wasn't a good idea and hope it'll come back in one form or the other in the next world, right now it just gives an illusion of a late game, and gives botting a huge advantage. With the cap you can tweak the balance in both pvp and pve, can make monsters that would take raids and strategies to kill, but that's a totally different subject for another discussion in another post.