You could use the "alignment" rules from Rolemaster Companion 4 (p.47)
Don't be put off by the name.
The Easiest way to outline a Religion is to decide on the alignment of the religion and what worshippers should not do. If a worshipper does something he isn't supposed to do he has performed a sin. Sins can be further divided into Minor sins and Major sins.
Characters maintain a SIN level (SiL) for everything they do; for a minor SIN they increase their SiL by 1, for a Major sin they increase it by 2.
The only way to lower a SiL is for the sinner to caster Prayer (Ceremonies List) for a period of time equal to five minutes times their SiL. This lowers their SiL by one.
People who can't cast this will need to seek out NPCs who can cast it and have them cast it for them.
The crucial thing about SiL is that it adds 5*SiL ESF to every spell roll, which is a nasty nasty thing for a spellcaster, so maintaining a SiL of zero is really important; obviously you can change how to reduce a SiL to other ways.
Example SINs for a power hungry magic god
- Using less that twice the number of PP to cast a spell (The rest are offered to the god!)
- Forgetting to pray each morning.
- Failing to sacrifice a magical item to the god this month.
- Destroying a magic item.
- Casting a spell for an unbeliever.
- Not donating any PP to the god that day.
With this system the channeling caster becomes obsessed with keeping their god happy; you can also tweak this system to add bonuses for negative SiL if they are on zero if they are good (up to a limit maybe) so they get a bonus to their ESF rolls.