For the topic of armors, I would humbly suggest a solution from one of the greatest games of all time: Phantasy Star IV. In PSIV, you would progress through the game completing quests and moving to new areas, mainly cities. In the new cities there were usually new types of armor available, but only for a couple of classes. In Example: There might be 4 characters in your party, but only 1 or 2 of them would be able to use the new equipment in a new city, as certain characters are unable to use specific types. This allowed for steady, linear progression, and felt very rewarding.