How to program organically evolving arpeggios with automation?

I am trying to do an effect with staccato woodwinds (and pizzi strings) where it sounds like the players are basically arpeggiating a chord slow to fast and back to slow. I'm using Logic Pro. However when I use Logic's Midi FX Arp plugin tool, you cannot automate rate *in between* standard rhythms; in other words, it must step from 1/2 to 1/4 to 1/8 and so on like that. The effect is very steppy and robotic. I obviously would like it to flow smoothly and more organically so I wish I could automate rate not synced to the project tempo. It would be also great to be able to automate smoothly the range or style of arpeggiation (1 octave to 2 and back, or up/down to something else etc.). Does anyone know how I can do this? Thanks.