5.11 CAMS. If you can't fit it in one of those you need to cut down on the amount of shit you carry. https://www.uktactical.com/product/511-cams-30-bag-ranger-green-16926
My wishlist still has all the gear but a lot of the gun parts are "item unavailable" so handguards, stocks etc. Sights and mounts are still pretty much there, lasers and lights are a bit hit and miss (probably depending on what else the store sells)
As far as the mag goes, any drum mag that works with an M4/M16 would be fine. For example https://www.patrolbase.co.uk/nuprol-1200rnd-electric-drum-magazine-for-m4-ar15-aeg
The pinion will either be a push fit or it will have a grubscrew which will no doubt be embalmed in threadlock.
If it's a push fit you'll want one like the "large vice" version here https://www.ant-supplies.uk/assorted-tools/motor-pinion-gear-tool.html because the type you have linked to will only pull the pinion off, it won't help putting it back on.
Thanks to an imminent inheritance I will be able to pay off my mortgage early. Obviously I've made all the right noises about investing the now disposable income wisely but we all know I'll be going through my wants list and ticking them off one by one.
Will power is overrated.
Ducati were bought by Lamborghini who are owned by Audi which is part of the Volkswagen Group. And their electrics are still made in Italy. Although the injection of some German cash does seem to have sorted them out a bit.
Personally I'd say get something with a bit more grunt if you're planning on using higher capacity LiPos. That one tops out at 2.5A so anything over 2500mA/h is going to take upwards of an hour to charge. I would suggest the SkyRC S65/Turnigy Accucell S60