I agree with bringing in lock picking or some other similar system -that does not involve blowing up the chest to spill out the contents-, but I don't think you need to add in a whole new class. Ninjas could use lockpicks (that take damage with each use) but a smith would have to make them. Tnt could be limited to being creatable only by engineers but only usable by miners (just because you can make it, doesn't mean you know how to use it; Ford made the first car, but I bet you they ran into everything when they tried to use it!).
This system could potentially encourage players to work together to:
(raiders)
1) breach the perimeter somehow, probably with the use of TnT.
2) protect one or more VIPs (ninjas, who will do the unlocking, and wizards who will carry the stolen resources out by porting/recalling)
3) hold an area while VIPs collect resources
4) extract any remaining VIPs with stolen resources
(town)
1) build a strong perimeter
2) create in-town defense measures, such as obsidian outcroppings (for ninjas/fighters to hide behind and ambush raiders), and watch towers.
3) strategize to successfully thwart enemy raiders
4) make hidden secondary measures for entering an area that is being held by raiders.
5) build a bigger town on the remains of the failed raiders.
(economy)
1) create more resources to sell to merchants that act as neutral third party buyers/sellers, allowing for further flow of money that does not require both players to be online (hiring an engineer for making circuits requires the engineer to be on, but he does not have to be on if he already made and put tnt on the market).
Yes, I am thinking about the few players who stay on later when there are not as many players on; they matter too.
People don't like playing games where they lose everything all the time, so there should still be some form of protection for items, but if there is too much protection for items it does make raiding somewhat unprofitable (even though you are going to earn takeover money for raiding the other town).
As for the War plug in, I can see it being abused by towns and raiding another town while they are all offline. Yea there may be a cool down, but that does not stop them from doing it in the first place; I cannot suggest any solution for that though.
Miner should not be able to make tnt, because more than one class having access to tnt is redundant and unneeded in a town setting.
Solo raiding a town should be VERY hard. Who do you think you are? You are not the big man in the sky, nor a flying spaghetti monster in space, so why should we make it easier for solo scrubs to raid our town while we are all offline? Making it easier for solo raiders to steal from towns completely negates the purpose of having towns in the first place, as well as the war system. Why join a town if some solo player can still just get in and steal everything? Ill give you an example of a solo raider.
A map or two ago I was a runeblade (I am wizard this time), and I managed to actually level up to a high level for once ( I know I am such a newb). Well I came across a town whos members were all offline, and they left their gates open. just let that sink in there... they left their GATES open. All the gates, in the ENTIRE town, were open. So I walked in and blinked to the top of one of the buildings, since the doors were all protected, and I let my self in through the unprotected entrances on the roofs. One building housed multiple people, and so after searching around I ended up with full gear and lots of resources. I started to get worried about them coming back online, so I used some of their redstone to recall back. LWC was used on this map, and I still found over eight chests that contained some rather valuable (and not so valuable) resources; note worthy loot includes several stacks of iron blocks (at the time it was valuable to me ok? I'm lazy), a nether star, and my new set of enchanted gear!
Now, even if that town hadn't left the gates open, I still could have gotten in with a bit of planning, but I tend to be too lazy for that.
TL;DR: People in towns tend to relax their security because they think they are safe, and thus end up overlooking some measure of security; which can end up leaving them vulnerable to theft, even If they use LWC on some chests.
No doubt there are flaws in what I have said, but since this is a suggestion thread go ahead and point them out for me.