To be fair, that is a thematic change from the original game. It is hard to imagine High Mage Aelis as mysterious figure who goes years without human contact, when he has a couple hundred assistants he needs to clothe, feed and help him cast realm spells.
Personally, I like this new direction - it fits better with the general feel of the game and in practice this has been in place all through RoE 2 (dunno about RoE 1) as you really need a court rating to be an effective caster. I'm not sure I would call it a core concept, but it is a change compared to the original game.
As a general principle, I think the roleplaying elements (training, story reasons for being able to cast realm spells, etc) need to be reflected in the rules. Also, the D&D 3.5 system seems to be something we are moving away from, started by Bjørn with the "tiers" introduced for skill modifiers and continuing with this. A single level in this proposed system reflects several D&D levels... enough for a couple of feats and skill points.
Perhaps to gain access to Domain Caster Level, you need to spend a couple of actions, over a period of time? 2 actions, each in their own turn?