By 'lower magic', do you mean magic is not as common, magic is not as useful, or magic is not as powerful?
I think if you wanted to just keep magic from being the 'instant cast' type that it is now, just up the casting time requirements for everything above 3rd level spells. That automatically keeps the higher level nagics from being very useful in combat, but allows mages to 'buff up' other members of the party. And some of those higher level combat spells can be 'held', can't they, so you can spend ten minutes preparing it, then just hold it until needed?
Most of the common 'battle' spells are 3rd level and below, so they still get to contribute to a fight this way.
To go the component route, just require that spells above n level require a special gem or something to cast them. The gem can be expensive (ballpark figure, 100-200 gp per spell level), or rare, or require extensive preparation. Spells remain easy to cast, but mages are more loathe to use them.
Divine magic can be handled the same way, with additional flavor restrictions. Can only be cast on certain days. Can only be cast in a temple. Can only be cast in a
certain temple.
The Book of Hallowed Might has a few ideas like that. Maybe healing only works at full strength on those who share your faith? Maybe it only works
at all on those who share your faith?
(Probably getting too restrictive, there...)
Just some ideas.
