once upon a time when I was dabbling in semipro TTRPG design, I put together a base class for Pathfinder RPG to fill what I saw as a notable void in the archetypes: an arcane guardian. my life took a turn and I wound up sharing it for free; for the curious, the final PF revision is here.
D&D 5e is a lot more flexible in terms of allowing armored wizards out the gate, and between that and a critical shortage of spoons it took me a while to port the class. but toward the end of 2022 it finally happened, with many tweaks since! (the revision number is a date, so you can see when the latest was.)
Iron Mage 5e r20240908 (pdf, CC BY-NC-SA)
currently designed around "legacy" 5e, but an update for the "OneD&D" revision is likely.
Had a few friends playtesting this over the last year, did a ton of revisions, updated version at the link above!