Sounds like a very simple option for me. I agree with OP!

I'm still waiting on my cash register sound when something is purchased though.

I don't think it would be too much voice work. I mean, it's one more line for each champion? It would certainly be an improvement over OWWNNNED, though that's just a placeholder anyway.

I like the idea, as long as the lines are thought through and spot on for each character. Some of you'r suggestions might sound kinda corny with the current "trailerman" announcer though

Thus, maybe it would be nice for each character to voice the kill sound? Hearing Veigar say "You see? I AM EVIL!" every kill would certainly put a smile on my face. The logistics of rerecording a single clip for each though, would be a nightmare I'm sure. Thought I'm sure multiple clips wouldn't go astray...

The multiple voice bit, by the by, is a good way to stop death-reward-sounds getting old fast; in dota I tend to use the sounds off option most of the time, it only annoys me later on. In another AoS (or MOBA, as we're now calling them) called Tides of Blood (Wc3 mod), every kill sound was a from a different set of voice clips, depending on which side and hero type (nuker, farmer, agi-hero killer) ot the kill. I know I tried to turn off my "ownd" voice over the first time I heard it...spent a good couple of minutes trying to do it too.