Foolproof? No, this isn't something you should fool around with!
Make backups of old (working) kernels. Carefully examine dmesg to see which device drivers you are actually using. Do some research.
PCMCIA is a standard for connecting cards containing useful interfaces, primarily to older laptops. It was replaced by the CardBus standard, and then promptly dropped, since most laptops started having built-in networking and USB, then got really thin and started removing ports.
SCSI is a standard for transferring data between computers, primarily used for connecting spinning rust and tape drives on server-class hardware... however, you need to be careful, because USB sticks/disks emulate a SCSI interface. Disabling support for SCSI scanners might be safe, but I'd worry about eliminating SCSI support entirely.