I hate losing items as much as you do, believe me. My best solution to cope with this, however, is to go with absolutely nothing in my inventory. Put the most valuable/useful things in your /chest. This way you can probably get it out whenever it's needed, like a bow and a couple arrows or something. If you can put everything away first, the only thing that you can lose after that is your XP levels, which can be easily grinded through /pwarp grinderpark or through killing mobs and people somewhere else. It might be a bit tedious, but trust me, it's very much worth not losing your items.
Make it if a player gets killed within 3 or 5 seconds of a tpa they don't drop anything and they keep their items.
~ @Kling
Make it so that they have invincibility for that 3-5 seconds, if this suggestion does go through. To make sure neither side has an advantage, let the person who let the first teleport to them also have invincibility as well, so that neither can get hurt for a small amount of time.
