I'm taking this means one could say that "starting with the character you want" really supports Rolling Advancement better than "starting with a Character that has 'room to grow'" (that was sarcasm),Agamemnon wrote: There are really three axis at play when you're talking about "player character power." The first is how powerful the character starts relative to the world around them. The second is how powerful the character can actually become before the system breaks (i.e. skills cap at 10 dice, or whatever). The third is how long it takes to get from the first to the second.
"Starting with the character you want" is an issue that is discussed on the first axis. Advancement rolls are an issue to debate on that third axis. As a result, advancement rolls don't conflict with starting character power, but they also don't impact it in any way. You could have random advancemnt rolls with characters that already began more powerful than anyone else in their setting.. or you could have it with characters pathetically underpowered for their setting. It's a design choice that doesn't directly overlap.
eg. Rolling for Advancement, in a way, necessiates being allowed to Start with the Character you want.
I certainly share the sentiment, by and large - in my system, i intend to give players the option to start as "Masters", which would be represented by a Skill value of 6 (on a range of 1 to 10, where at Rank >= 7 you are considered to have contributed to the advancement of the discipline and at 10 you are a living legend).