Ok - some answers to your questions......
V6 swap-in is possible with some effort.
exhaust hangers same
propshaft same (ish) manual V6s have a larger front coupling, but you can stick with the small one if you've already got the gearbox installed.
manual propshafts longer than auto
manual gearbox will allow a V6 no problem
engine mounts on subframe same
electrics. The only way is to start from scratch and make an engine loom for the V6 using a donor loom from a salvage car. There isn't a wiring diagram for the 2.6-Siemens style engine ECU, but its all pretty simple stuff. Just trace each wire interface with the car and replicate. 2.6 is of course drive-by-wire - so there's the added complication of the pedal interface. Note just running a 2.6 with 2.5 electrics is a bodge and shouldn't be attempted.
2.6 V6 is just about the worst of the range for power and driveability. Drop it and get a 3.0.
Don't remove an ABS - EVER. Just supposing you had an accident - how would you answer the question "so you've made your car less safe by removing the ABS.....?" You can add an "off" switch by all means, but don't remove it.