Cockers are always a little more gas hungry than most other markers as they work at higher pressures than most.
Wrong, and wrong. 'Cockers aren't usually all that gas hungry, and they don't work on higher pressures than any popit-style guns. Your input pressure will be between 200 and 300 psi, LPR at or below 90 psi. Your logic is convoluted anyway, as LP is far less efficient on air than HP. Remember, low pressure = high volume. You will need a larger volume of air at a lower pressure than you will with high pressure.
It might seem strange but go for the LPR first, you'll achieve much more constant velocitys with it.
The LPR doesn't really have any effect on velocity: all it does is control the back block and bolt, it does not in any way change the amount of air released by the valve and out through the bolt to propel the ball, so any improved consistency you're seeing in changing your LPR is purely placebo effect. Your main reg will help you much more with velocity consistency.
To the OP, it sounds like your gun is pretty much functioning fine, no? So what's wrong with that? New trigger for comfort, new feedneck for functionality, maybe a new barrel, what else do you need? You could always half-block it. There's a pic of a half-blocked Karny at
www.halfcocker.com on the main page, it's absolutely secksual (yes, with a "ck" even!). I'd recommend not fixing what isn't broken, spend your loot on paint and blow people's heads off.