Let's really look at the facts, and stop throwing useless items at this person.
All A3000's had a 68030 processor and a floating point unit soldered to its motherboard. The A3000-16 uses 68030 and 68881 @ 16 MHz while the A3000-25 uses 68030 and 68882 @ 25 MHz.
(1) At best case, it has a Buster04,DMAC02,and Ramsey04. Your talking about NO possibility of 060 without the upgrade chips, and a cost factor of =/- $130 USD.
(2)Has flawed on-board SCSI controller chip: =/- $30 USD
There are several problems that can occur when adding additional SCSI devices to the SCSI bus on the A3000. Most common are random SCSI bus lockups, especially with CD-ROMS or tape drives, and random checksum errors when copying large files between devices. These problems can, in most cases, be attributed to the WD33C93A SCSI controller chip in the A3000. Most, if not all, A3000's shipped with the WD33C93A-PL 00-04 chip revision. This chip had known bugs when multiple devices were present on the SCSI bus. With a single device, problems rarely occurred. As soon as the user started to add devices to the bus, the problems mentioned above would start to appear. The WD33C93A-PL 00-08 chip revision addresses and fixes the above problems.
(3)AmigaDOS2.04-3.1 can use drives less than 4.0 GIGS only, and sometimes, only 2 gigs is ideal. (See below).
It is not too difficult to understand what causes the 4+ GB problems, though perhaps a little bit technical. Simply put, AmigaDOS uses 32-bit pointers to reference positions on a hard disk and therefore can reference a maximum of 2^32 bytes or 4,294,967,296 (4 GB) - Note that, with some older SCSI controllers and devices the limitation is actually 2 Gigabytes.
So, for a 2.04 system, I would recommend a 2 gig drive.
(4)Forget the soldering of the battery. Just nip and cut the battery off. Leave the "ears" that stand upright. Solder new leads to these 2 ears, and lead them back to a new location.
Personally, I put a replacement battery in a small plastic bottle, and tied it off away from the motherboard.
So, if your going to be helpful, tell this user the facts. Don't throw "do this and do that" until he can resolve the basic problems with this 16Mhz machine. And, yes I do know that most revisions of the 25Mhz board shipped with these old chips installed. I am not trying to rain on your desire, but start with want will stablize your system.
