Careful with the terminology: in Pyramid, a sequence is a set of track mute-states and it’s speed can be changed with the BPM effect. But quite obviously that’s not what you’re talking about here.
I don’t think there’s any easy/obvious way, but here’s a wacko idea (that I certainly haven’t tested so buyer beware): maybe you could change time signature to half/double the playback speed in polyrhythms-mode, and if necessary, use old-school consolidating to capture the result into another track playing in the original time signature. Or something along those lines…