I personally don't have a problem with the stat boosting rituals. They are not as inexpensive as people propose, and they are fraught with risk.
That being said, I'm pretty firm on the idea that ritual spells are always cast under stressful conditions. The only way to mitigate the botch dice are: Mercurian, cut the risk of botching in half because they reduce pawns of vis necessary, Cautious Sorcerer which removes 3 botch dice, The Golden Cord, removes whatever score there is in it, and Spell Mastery. Without spell mastery there is always at least 1 botch die. Mercurians get a big advantage here, couple it with cautious sorcerer a golden cord score of 1 and mastery of 1 they can cast this spell without risk of botch, but that's 4 virtue points and the effort of finding and binding a familiar... The mastery would be done via practice (which I can see being done without using vis), taking up another season.
So, that's 10 botch dice on these rituals, which is quite a risk. And while the guidelines do allow for them, I'm going to say House Mercere retains all the texts on spell mastery for these rituals, and they come at a high price, probably not worth paying...
More than likely a botch will cause something like what's happened to Ysebrand. It gets worse from there when you do more than a single botch with 10 pawns of vis. 