Hey, it's good to see another person on GT playing some fingerstyle. :)

The moving bass line is the hardest part of learning to fingerpick. If you're having trouble coordinating complex lines, it sounds like you need to briefly return to the basics. Mentally divide your picking hand into two parts. Your thumb is independent of the other fingers. When you're fingerpicking with them, they have their own roles in a "call-and-response" sort of arrangement; the thumb plays a bass note to define the chord, and the fingers elaborate on that bass note with some higher stuff. I found that the best way to start was with a metronome. Set it to a nice slow simple timing, pick a basic major or minor chord, and just start playing one bass note on the first beat of each bar. When you fall into the rhythm, you can start elaborating on each bass note by "responding" with other notes played by your fingers. Don't try to get too fast or complex too quickly - you may even need to start with just one bass note and one corresponding higher note per bar. Hopefully, this will get you into the swing of coordinating your thumb and your fingers while fingerpicking.

Don't know if that was of any help :o, but yeah. Enjoy.