Changing Spacing Between Keyframes

Copy your footage, open After effects and create a new composition, paste your footage, press U to reveal the keyframes, select all the keyframes, press Alt + drag the last keyframe, this will allow you to "scale" the keyframes in relative to time. After that copy your footage, switch to Premiere, and paste.

It looks like a long process but if After effects is opened it's a matter of seconds

i think it's gotta be manual but I don't think it'll be that big a deal.  You'll probably want to expand your effects control window for the full width of your monitor,  put your playhead at the second keyframe.  select all but the first keyframe (you can use the mouse to marquee them) and "cut". command-x on the mac, control x on windows I think.  go down 4 frames and "paste",  select all the keyframes from the 3rd, cut, go down 4 frames and paste...  repeat and rinse...  make sense.  Duplicate your sequence before you do this in case this doesn't work...  but I think it will.  Maybe someone else has a better idea...