But the Druid has proficiency with Medium armor. Normally, all medium armor is all or mostly metal. I put those two facts together, and I see a story hook, an adventure in the making, not a reason that a druid will never have a breastplate or half plate of any kind. It's a potential challenge to overcome, after hard work and RP and a pile of gold. If said druid took the feat for heavy armor, and does some really cool stuff on the way to putting together plate armor made from monster parts, I think they've earned it.
I'd agree, but not for Organized Play. That level of flexibility and RP rewards are possible in homegames, but not in OP.
It sounds like you want a type of Organized play that can reflexively respond with individual PC/Player rewards based on either individualized "mission/adventures" or built-in flexibility within the scenarios (and thus the campaign) as a whole.
You're struggling with what I struggled with when I had my first Organized Play experience with Living Greyhawk. I developed a character concept that relied upon aspects of rules that I had no idea would never be fleshed out within the paradigm of organized play. Things like herbalism, crafting unique items, entrepreneurship... None of those things had a place at the time. And some of them still don't--even though they are clearly articulated as potential options in the PHB. I came looking for great roleplaying opportunities that impacted the development of my PC, and had to redefine what roleplaying meant in order to fit within the context of how Organized Play worked.
I started to embrace the OP experience for what it could offer me (which, in all honestly, had
nothing to do with the quality of the gaming experience or my PCs empowerment or development or capacity, and
everything to do with a social circle of gaming friends and opportunities to play adventures with them). I changed what I expected from it, and along the way developed a deep understanding of how a homeplay campaign could incorporate so many aspects Organized Play's system couldn't. Now I have both in my life and I let both of them be rewarding for different reasons.
To be completely blunt, Organized Play can be a whole lot of fun when you don't approach it with the same expectations you would have of a homeplay campaign. It's a continual process learning what the difference is. It's not the normal D&D that's portrayed in the rulebooks. It's a unique and specific flavor of the D&D experience. By default, there are whole swaths of rules that aren't relevant and will never apply to OP because they can't. Entire portions of the rules have to be re-evaluated contextually given the hundreds of DMs, thousands of players, and international locations of portable characters all in a single shared world. I came to realize my DMs were really "proxies" facilitating a gaming experience that was way bigger than just my table. It's my feeling that the nature of Organized Play doesn't allow for the individual reflexively responsive RP rewards that you're seeking. But it can be a lot fun for what it is, if you embrace that and the intangible rewards that come with the experience of playing.