So finally ended up modifying the canteen pouch. I'm a bit cheap so I just used what I had laying around. USGI Compass pouch on the front is about perfect for an altoids tin and a space blanket. Additionally the velcro on the water purification tablet pocket has been extended out so I can overstuff that as well.
Managed to squeeze in an ESBIT stove with 4 fuel tablets, RSK MK5, and a couple of drink packets in the main pocket
In the water purification pocket I have 8 purification tablets, a firestarter and tinder, mini clif bar and another drink flavor packet
In the pocket with the canteen (not shown) is of course the stove and cup, as well as a couple of instant coffee packets and a poncho. I used to have 550 cord in there but ended up using it.
The compass pouch is sewn on at 6 points with 50 lbs braided spiderwire. I'm going to add two more attachment points for a shoulder strap soon.
Regards