Those elements do not demand alignment systems. An alignment system is sufficient unto itself, whether or not they're RP only or have actual mechanical ramifications.
My "D&D" sims in Fantasy HERO had no real alignments- HERO has none- but did have Paladins, Devils, weapons that didn't work for certain beings or only against certain beings and circles of protection. How? By redefining how things worked within HERO's framework.
For instance, a Paladin would probably have a limitation of a Code of Honor and another that was a Sacred Vow. Violating the Code of Honor might only have political/RP consequences, or might manifest itself as losing the benefit of Contacts and having negative modifiers to Presence based checks. A Sacred Vow might be done similarly, or for real teeth, would be an operant precondition on all of the Paladin's "holy powers"- violate it, lose all your powers.
Yada, yada, yada...