Ok, writing this ‘off line’ so apologies if I miss anything!
Weapons:
Drones: A weaponised drone (eg rotadrone) counts as 1 weapon (including mounted weapon), an anthroform drone counts as 1 weapon (without weapons), but will get a free melee attack, and you can give Arthur one of your other allotment of weapons…and nothing to say you can’t pick up weapons once you are on the metaplane!
Hellhounds: Yes, Al2 will clearly count as a weapon! Guide dog…sheesh

Grenades: You can take a bundle of assorted grenades as a single slot
Ammo: For various reasons (see below) your ammo can be ignored!
Equipment:
Full armour can include a helm as one ‘equipment slot’ …but a shield is a separate one! It’s logical to me at least! If you want Arthur to have ‘worn armour’ you will need a slot for that too (anyone would think I don’t want you to bring him along?!?

Jack, if you think I am unfairly penalising you here (and I can see why it might!) I might reconsider the weapon and armour thing!
A spy drone counts as an equipment slot…but I might be persuaded that a small number of identical drones count as a single slot…
Nobody taking a commlink? Better hope you don’t get separated!!! Robyn’s deck obviously functions as a commlink too but she’ll be talking to herself!
A kit, eg a B&E kit or a mechanical toolkit counts as a single item
Metaplane Metaphor:
This is going to be loosely inspired by Bernard Cornwall’s Arthurian books…so Isaint will look a bit like a Roman Centurion in his getup rather than a mediaeval knight! Plus the Keltiad books by Patricia Kennealy… the latter is a blend of Celtic stuff with Space Opera…so your firearms will be ‘lasers’ …it’s less cheesy that it sounds, honest…bit Star Wars esque…