I know that there is a current way to do this but its a pain in the butt.
My suggestion is to create the "Federation Cargo Authority".
Give them a booth at all the Federation Starbases, like on ESD build a booth on to the current booth that has the Fleet Ambassador in it.
Next players can go up to the "FCA" and when they want to transfer loot to another one of "their" characters they can pay a combination of EC's and Dilithium, or EC's and collected resources like those entertainment provisions ( basically EC's no matter what but a secondary "Trade" of resources) but no C-points. Depending on how much you want to send depends on how much it will cost you to send it.
Once you log on to your other character you get a notification that you got a "package" you then look into your inventory and see a clickable package that unzips giving you all the sent items.
This unique system would also offer a service were you could send "rare" and "uncommon" for an additional fee. And during certain "breaks in the war" would be willing to accept "very rare" items fro transfer.
This in a way would make the "FCA' like Fedex of the 25th century for the Federation anyway.
For the KDF the Ferengi could run a similar operation, call it "Nagus Express" lol
Anyway I think this system would be interesting to see in-game I also think that it should not be allowed to be purchased with C-points since this could help create a "sink" for EC's and other resources.