My suggestion is a simple one and I will keep it brief. I suggest adding the plugin death chest to the server it a very simple plugin for a problem lots of people have had, dying to close to clear lag and items despawning with this plugin it will create a chest with a timer so you never have the misfortune to die and lose everything to clear lag.
I am not saying it for unlimited time but let's say you have the misfortune of logging out in /fly, you log back in not knowing clear lag about to hit try and grab your stuff and it all despawns. Then all that stuff you worked for is gone, just forever because of clear lag, minecraft has a natural despawn timer for items, and I am in no way trying to circumvent that but if it a plugin on the server that is to help with lag despawns stuff like that it can kinda ruin your experience. As to chirity if I read the stuff on the plugin page it can be locked to players so I am assuming maybe if you died in someone else town it might just override the town perm for that one chest with your inventory to get it before the timer makes it go poof. Could be wrong though but could be something to test on the dev server if the plugin is accepted.
It does not cost much to purchase the first donor rank. With that purchase comes the perm for /fly, which will prevent fall dmg, as well as the perm for /back, which returns you to your death point and lost items. As was mentioned, this is partially a survival server, so you need to be aware for any dangers. And with those extra safety measures that come from donating, it's a lot harder to encounter your problem.
Even if you cannot purchase a rank yourself, people are often willing to pay the $10 in exchange for in game money. Keepinventory will not be added to the towny world in the forseeable future, so I would suggest taking advantage of your /backpack for valuables more often until you can acquire Atlas rank.
ThatOneTyler making it so only donors have keep inventory is kinda shady and feeds into watson was saying of making life to easy, I suggested this plugin to prevent people when they die from typing /back or if they have a home to get to death point and clear lag eating the stuff before they can get to it. Clear lag is necessary for the server to not lag so if we can't get rid of clear lag then the suggestion of death chests is for people who /back with the misfortune of not seeing clear lag to watch everything disappear before them.
Though I do see where you are coming from with your idea, I do not think it should be implemented. Every time you use /rtp or /back, you are signing up for the chance that you may be in a situation where you will die. To counter the chance, you need to use basic minecraft survival skills, as well as using plugins to your advantage. For example, if you rtp to the edge of a cliff and accidentally step off, fall, and die, there could have been preventative measures taken. You could have gotten better gear to prevent taking as much damage, or grind for acrobatics in mcmmo to reduce fall damage/avoid taking it completely. The same logic of using vanilla skills combined with mcmmo can work for most scenarios, and therefore removing the risk of losing your items to clearlag would in a way render some of those essential skills more useless.
Just my two-cents
I am not trying to circumvent death completely only bad luck of dying close to clear lag with /back or going to your home and watching CLEAR LAG eat your items. I don't see why everyone thinking I am trying to make it impossible to lose items this just prevents stuff from despawning from a plugin on this server.