Li Shenron
Legend
For specialty priests I could actually see specialty domains. Rather than taking the knowledge domain a priest could take the Mystra/dweomerkeeper domain, it may even just be a current domain which is modified to diferentiate it.
In general all subclasses can work great for representing specializations, the only problem is their fixed starting level, even more in the case of domains since they have to be chosen at 1st level. So they are really not very good to represent an "elite/prestige" group... if the Mystra's Dweomerkeeper are supposed to be an elite group that only the best can enter, then using a domain to represent it means that you enter it at 1st level, so you must be a 'chosen' since the start, but it can't happen later on in the campaign, and it can't be based on story requirements...
Unless you consider one of these options:
- a domain that can be taken later in the campaign and replaces the starting domain: for example you have the regular Knowledge domain, then at some point in the story you are invited into the Dweomerkeepers and gain their specialty domain, but lose the Knowledge domain. This requires some ret-conning, but we already have a precedent in the game (the Paladin Oathbreaker).
- not a full domain but rather substitution levels i.e. some specific features that will replace the benefits of your current domain and/or base class features, at specific levels