Better MR Items

We've got some decent armor items (although as a Rammus jungle, I'd LOVE some more armor-based items that don't reduce the attacker's speed or have other silly auras, but I digress)... we've got some reasonably offensive armor items (Sunfire, Dead Man's), and some offensive AD-based MR items (Merc Scim, Maw, and that neat newish on-use channeled shield AD item I have yet to see used successfully for that purpose in any game)...

Not a whole lot of offensive MR items for tanks or anything other than a Nocturne, Kled, or other AD-tanky hybrid.

Banshee's for Karthus-proofing, Spirit Visage if you're Renekton. Abyssal if you're a mid-lane tanky mage or just getting your butt handed to you.

That's about it.

Where's a nice MR item with a Bami's Cinder built in? Where's an item that builds stacks and deals damage, like the MR equivalent of Dead Man's? Where's ANY MR ITEM that does ANYTHING except for give you increased health regeneration?

Where's the Thornmail equivalent in MR, with a magic reflection % damage, or a spell-reflect on-use, or something equally full of majesty and general badassery?

What if I'm playing something like Sejuani tank, where sure, Banshee's is an acceptable MR item, but aside from that occasional shield it's really doing nothing extra for me. It doesn't contribute to my kit or to the team, my W scales off my max health and yet Banshees only gives me a measly 300. Sure, you'd argue that 70 MR is actually a huge amount, and it IS, but I'd vastly prefer 50 MR and something more useful. Building Abyssal isn't going to be a HUGE game-changer if it's my only AP item.

Building armor has so many options for situational items, but I'm just not feeling the same flexibility for MR. In a game where I'm tanky and the enemy team is full of mages, I get this overwhelming urge to just buy the token Banshees. Building MR tank shouldn't be so painstakingly boring and single-minded. We have multiple options against AD users... so why not provide some tank MR items with more utility, or... well, FUN?