I think the enchanted backpack should spawn consumables like potions every so often, like 25% chance a turn to spawn a healing, growth, or speed potion, rather than global resources.  After all, a crystal is much less useful to a roaming adventurer than a health potion.  The golden belt actually producing gold is a spiffy idea as well.

I'm not sure if it should affect global income or metal and crystal income.  Just enough so that it provides a good base income, with possibly a bonus per level (feeding off the potential of the hero).

I like the idea of getting potions for the Enchanted Backpack, but I think having 25% chance is a bit high.  Maybe 5 or 10% of getting a potion (or maybe less), with a higher chance of getting the less expensive (read: less powerful) potions.

Or a combination solution could see the Enchanted Backpack come up with a random resource (say 10 crystal of 15 gildar) OR a potion.  There could be a table with different probabilities, and hero level could influence too.

It would be useful at the beginning of the game and at the end of the game if the items would affect the global income and it would make the tax rate not meaningless.

Yep, only one effect should apply, because otherwise you would get the warlock + evoker IV + staff of souls + a few shards effect

My rationale for the low % was three-fold:

1) It's an early game item, low-tier

2) It takes up the cloak slot, which has very few good choices until the mid-game

3) I had to make it so that it wasn't exploitable, say by healing yourself over and over.

There aren't XML tags to do it in strategic mode, unfortunately. But I'm not sure I would have put it in strategic mode even if there were. Having an item slot that is usually taken up by combat-boosters provide a strategic bonus is dangerous, because it encourages micro. Equip combat cloak for battles, at every strategic end of turn, equip the backpack.This is why the Crown of Procipinee is an accessory instead of an item that takes up a slot. To me that is boring.

I know Derek has spoken out against city-boost items but I think there's a niche for heroes passive in cities getting bonuses from items.

it can provide +1 armor and two virtual healing potions for tactical combat.

for global, it shoud heal owner, 10 hp per turn will be fine. 

virtual == not separate item, soo you cant store them or sell or share in party, but in tactical combat anyone with backpack can heal himself two times.

this will make backpack super usefull for anyone just like it was before. 

You are a Master Modder, Heavenfall!

It's a pleasure to browse through the code of your mod and see your great abilities.