MamoWrold’s Mathias Möhl shows how simple it can be to modify a ton of preexisting keyframes in After Effects, suing KeyTweak.
The script will allow you to change a few keyframes, automatically changing the rest of them. You can modify all of the keyframes in your work area all at once. The script will even allow you to create an in and out fade for the changes, which will help to avoid abrupt animation.
It is not quite as robust as a spread/dope sheet would be — but until After Effects actually gets a dope sheet (if ever), scripts like KeyTweak work really well.
In Mathias’ example, he shows how you can modify a bouncing ball animation with KeyTweak. The script is available on aescripts + aeplugins under “name your own price”.