I assume this thread will illicit an official response from WGT eventually. Here's my second hand understanding of why they went with only 30 or 90 (wasn't there for conversation but got the update from a reliable source). They started with only the addition of the 30 sec timer to test and see if if would be feasible even with some meter issues and such. I assume the plan is to implement a few other variations after they've worked the bugs out with the initial change. I'm no programmer so I don't know how much more or less difficult it is to add a few other choices. All in all it's a sensible change that wouldn't make sense for them not to improve on it. Just takes a little time.
That being said, I agree wholeheartedly with the 15, 30, 45, 60, & 90 sec increments. The 15 sec will be the sadistic one that no one will use for REAL ranked rounds, BUT it will offer some good times for community organized tourneys &/ or just a group round with special rules. (Such as beat the clock/ no aim/ use the line/ set up/ club given to you by default, etc) All the rest of the increments can be used fr regular games, 30 seconds is great with a flawless meter but a few hiccups can make it tough. I played a challenge match with someone earlier today on 30 sec setting & we made it through with 1 timout a piece.