I was thinking about this. I don't desire the ability to replicate the vinyl crackle or warble, but as far as the compressor itself, there surely has to be a way to recreate it. Perhaps you could take a audio of known quantities and run in through settings of 1/4 increments and measure the results. I'm assuming the compressor knob amount controls both ratio and threshold.

Anybody else have any thoughts? I know folks that use other DAW's and use the SP's just for that effect.

You might come close with say in Ableton using a saturator with a limiter or something. Oh in reason if you use the "Energy" mastering preset with a scream saturation setting on a bus you can get pretty crazy pumping and what not. Just have to experiment with "Wamth" Plug INs and Limiters and Compressors. My fav part of vinyl sim is the wow/flutter which is why im interested in this.
http://www.snazzyfx.com/wow.html

for starters, i'd suppose you'd want to go with a tube or tape saturation vst, then run that into a compressor with a very short attack and moderate/short release. The threshold setting will determine how extreme the effect is.