So I'm working on a campaign setting in which all magic casting has been restricted to either its arcane school or its divine domain, thus arcane casters are specialists (by default). This makes the choosing of specializations and gods / domains a very significant decision in the campaign and ensures that there are no such things as "generic casters". The servants of the Gods are specific and much more unique, the mages are distinctive from each other and an Evoker plays differently than a Conjurer, etc.
This restriction only applies to spells at 4th level and higher, so lower level utility spells are not impacted.
There is one issue I'm running into with Divine magic however, many of those spells are not typed by Domain. Given the setting I'm describing are there suggestions on how to address these spells? I'm thinking of having them cost double spell slots and just letting it go at that point. Thus there is still some flexibility and it does not shut out 90% of the divine spells due to a missing mechanic.
Thoughts?