I can understand how you feel, but I think you are comitting a classic overthink here.
Cincy has allowed the 2nd fewest points to fantasy WRs, while the Niners have allowed the 6th most. Between Maclin and Nelson, this week I would go Maclin unless he is looking gimpy or something.
I haven't been following the MIA situation, but it sounds like you are speculating about Bush starting over Thomas. Could bite you in the rear.
I would probably stick with Maclin. viewtopic.php?f=19&t=500650