With standard HTML5 video, our options are no-buffering or whatever the browser decides. Most browsers now at least limit the amount of video they download, instead of just downloading all of it.
The work we’re doing to support adaptive video will eventually have buffer control, using the browser’s new Media Source Extensions, but we’re not there yet. And that will probably only be for the HLS and DASH video formats.
The 1s buffer appears to be hardcoded, so there’s not currently going to be any top-level player options you can set to change that. While not ideal, you can always modify and build your own swf. Also you can submit an issue on the swf repo requesting that be exposed.