On my Escom A4000T (Commodore produced only 200 A4000Ts) there is an addon thats attached to the Disk Module and supported by silicon. I've been told that I would have to remove this addon if I wanted to remove the standard 880k floppy drive and attach a 1.76m floppy drive.
I recently bought one and will install that on my A4000T.
To address your earlier message, A4000T's have lithium batteries stock. they do not have the leakage problem of the earlier rev A4000's. the 4000T's lithium battery is just soldered in.
Some 4000t's had a small board plugged to the floppy pin header,it was just for using a pc floppy in them(many came with sony drives). later ones came with ugly hacked floppy cables instead of that little board. Any 4000T can use a High density drive, you just need a good cable that hasnt been hacked. no changes need to be made to the disk board other than removing that small adapter if its present.
Mech