Yep, battery charge indicator would be useful. I suspect if Canon were truthful, they'd tell you that recycle time is the de facto battery indicator.
I have absolutely no clue why there is no battery meter - probably a technical problem because the power flux is so dynamic it's hard to get a good reading on the charge (and because all batteries have different discharge curves)?
Btw Canon *does* say the recycle time is the battery meter, as far as I remember it's there in the manual in the cfn description to show the slave "charge ready" status either by the red blinky or just the small light on the back.
An overheat warning might also be helpful to avoid damaging the flash.
Um, the flash get disabled if it's running too hot, doesn't it?