Ditch the passthroughs (I did) With bigger batteries you don't need a PT
I like to have one so I have an A/C powered backup device on hand. But I admit.... you're correct (I dislike the cord anyway) that 99% of the time I don't need/want it. Of course, the mods I use have swappable batteries too so there's always a set or two charged and it's a 10 second swap out for the 14500's. No stupid cord hassles.
As to the types and fixes:
1) KEEP JUICE OUT OF THE BUTTONS!!!!. Many fail-on with a wet shorted button... then the protection trips.
2) Tape on the end like mentioned above (for those with a non-removable cord). Strain relief on the cord.
3) Types of PT's ... there are two types ... 3.x volt PTs with an in-line battery that trickle charge via a USB connection and 5 volt "direct" PTs that run off a 2.0 amp or better A/C -> USB adapter/hub/etc (NOT COMPUTER!).
Since the OP said that he/she wanted 3.x volts..... I'd go with an eGo type battery with a mini-usb connector on the end so you don't get the strain problem and still have a fairly-fat battery for walk-and-vape action.