I see your point, but Eternal Resolution seems like an exception. All the other armor-only rituals are things that directly effect armor. If it was more uniform, Empower Warrior should be weapon-only, Counterspell and Magic Evocation should be spellbook-only, and so on.
Having more -type specific rituals (I'd love to see 2h, small/short, ranged specific rituals) is great and thematic, but they should apply to the -type they are part of. Nothing about Eternal Resolution is tied to needing to wear a physical suit of armor.