House Rule? Super Focus/Super Restriction

We were wondering about a possible House Rule modification for our next saga, and wanted to see if anyone here had tried something like it and if anyone had any thoughts on how to make it work, if it could work at all.

Essentially, some players want to try out some more wonky character concepts that stretch the limits of normal character creation. Essentially, they want to creat Super-Major Magical Foci, balanced by an extra Super-Major Magical Restriction or Necessary Condition.

The one which interests me the most is a consummate Columba (The Columbae are the Warding Specialists of Wales, as described in HoH: Societas (Ex Miscellania). This maga would have a Magical Focus that applied to any Circle/Ring spell (!), but which carried with it the extra Restriction: Not Circle, that is, the character could never create a spell or effect, even spontaneously, unless it either was a spell to draw a circle (with no other effects, so Scribe the Perfect Circle would be OK, but Ring of Fire would not) or it had Target: Circle, Duration: Ring (exception for Longevity ritual). This is in addition to the normal up-to 10 Flaws needed for character creation. Essentially, this is a +3 Virtue which, like Diedne Magic, must be bought with +6 in flaws, with the extra +3 being a Major Hermetic Flaw.

It would create a character capable of very powerful wards, passive, defensive spells and economic spells (Circle of the daily Orchard etc.) but who was massively limited (Very few applicable rituals, utterly reliant on traps and static spells for combat, very limited mobility and a host of very useful spells off-limits.)

I personally think this could work, and would be really fun to have in-saga, as the player would have to think of creative ways to excel within the limits of circle-ring magic. Its certainly an intriguing character concept.

Thoughts?

I think the restriction is too extreme.

The idea overall however, seems good. I think a "normal" level extra restriction Flaw should be enough. That still makes it a a Virtue worth 6.

Have you included Hermetic Geometry , Minor Mystery Virtue (page 93 , TMRE) in the package?
This includes New Target: Arcane Circle and New Duration: Arcane Ring on page 96.

Naturally. That's the reason the player wants to include the ability to create circles as part of the allowable magic, to allow creating Arcane circles and Scribing the Perfect Circle.

This, of course, must be bought seperately at character generation, or learned as part of a Mystery initiation. I'm thinking the former is more practical.

The player is also thinking of buying the Craft Amulets virtue, which could work well with the warding power.