No. We need that Xpresso, and a lot of it has been carefully formulated to achieve the sort of results that would be fabulously difficult to get with keyframes alone.
I really think you should keep that.
I am away on client work for a lot of today, but will look at it again, and the possible solutions tomorrow.
However I have established that this is actually a 105 frame loop, and I am conducting all my experiments from frame 0 to 105, and currently seeing if I can get you what you want by keyframing the range mappers in the Xpresso (not quite on a frame by frame basis yet, but it may come to that !), with 'some success'.
When I resume tomorrow I will be able to give it some more time, and find out if this will work here or not.
CBR