My idea is a Jerbiton maga (went with maga because of the Mystery cult /templars, read below), who has Hermetic Arithmetic and all her spells would be rotes. My "problem" with this is it limits the level obviously, but the challenge I guess is, how much bang for your buck can you get from rotes?
I would take a Minor Magical Focus in Rotes - I believe minor is acceptable, because though it covers all rotes, the focus is necessitated by another minor Virtue and covers only small effects in general.
The other side is the Mystery Cult, which I would base on this (Real life description):
"Ermengarda of Oluja, along with her husband Gombau joined the Order of the Temple and donated land. They were clearly shuffled off into separate houses, and Gombau disappears from the record a few years later. Ermengarda, though, is unique. She is noted in documents as a Sister of the Order. Not a lay sister, consoror or donat, but as a sister, the presumed equivalent of a full brother. This again is astonishing to me, but there was more to come, and it blew apart all my preconceptions of the Templars, for in the historical record, Ermengarda is referred to as a preceptrix, commanding the house of Rourell in Catalunya. So not only do we have a female Templar which is forbidden in the rule, but she is no peripheral figure. She is a mover and shaker in the Order of that region and even commands a small Templar monastery."
and
"During the 12th century, the Teutonic Order (derivative of the Knights Templar) accepted women as ‘Consorores’ (“Sisters”) who wore its chivalric habit and lived by its Rule. These Sisters were in active service of hospitaller functions, but not military activities, and multiple convents were formed under otherwise “male” military Orders.
In the 12th century Order of Saint John (Malta), women were given the title ‘Soeurs Hospitalières’ (“Sisters of Hospitality”). There were chivalric Hospitaller convents in Aragon, France, Spain and Portugal, until at least ca. 1300 AD, and in Buckland England until 1540 AD. The Prioress of a convent was given the title of ‘Commendatrix’. [10]
Also in the 12th century, the Order of the Hatchet was created by the Count of Barcelona in 1149 AD, for the women of Tortosa in Aragon, who defended and freed the city when the battle-worn men could not find reinforcement soldiers. The women were all made hereditary Dames of the chivalric Order, and thereafter were treated as female military “Knights”. They were given the titles of ‘Equitissae’ (from ‘Equites’) and ‘Militissae’ (from ‘Milites’) [11] [12]
The earliest use of the title ‘Militissa’ as a “female Knight” was the Order of the Glorious Saint Mary founded in Bologna, Italy in 1233 AD, and approved by the Vatican in 1261 AD, until it was suppressed by a later Pope in 1558 AD. In France, other chivalric Orders of women were founded in 1441 AD and 1451 AD, granting the French title ‘Chevalière’ (feminine form of Chevalier) or the Latin title ‘Equitissa’. Continuing into the 17th century, the female Canons of the Monastery of Saint Gertrude in Nivelles were “knighted” with the titles ‘Militissae’, and were given the accolade of dubbing with a sword at the altar. [13] [14] [15]
In Old French since the 14th century, women held the title ‘Chevaleresse’ in connection with acquiring a male fiefdom conceded by a man, or as the wife of a Knight, and the title ‘Chevalière’ as a Dame of an Order. [16]"
So a mystery cult of Sisters (and brother magi) of the Templar Order with ties to them. This is where the dominion things would come in - like virtues and maybe new target, ranges and duration, maybe even initiating Powers as spell guidelines.
I would probably go for a Jerbiton, who finds beauty in aligning with God...