I think Darren's experience is a great clue -- be flexible. If I was trying to do what you are, I'd print out the train times between all these places. Then I'd prioritize them based on what's most important to you and which ones are near each other, and start down the list without being too locked into keeping a certain schedule.
We've done something similar in Italy, when we felt like we'd seen the sites in the town we were staying, and took day trips to nearby towns and it worked out great. I think the problem comes when you put yourself under pressure to get to everything on your list.
One thing to keep in mind is that if you're staying in Arles, you can see quite a bit either early in the day (such as the morning market)or in the late afternoon/evening, after returning from a day trip. That will help with train schedules.
My feeling about Provence is that you'll probably enjoy your time no matter where you go. Happy travels.