Just boosting limited appropriate stats is far more plausible. It would vary saga to saga based on how common stat boosting magic was, but some degree of it being available for a given mystery cult is perfectly valid.
Even serving as the Mystagogue, my character only went to Pre +3 (from +2 when made) despite having rituals that could take him to +5. He has Flawless Magic so no chance of botch, but it just does not seem worth the 22 pawns it would cost.
My magus has used rituals to get up to +1, which was the limit on the lab text version we got. (Negative Perception started to annoy me.) He has the lab total to learn the level 60 versions, and flawless magic too, but he does not have the casting total. He might still, of course, only 25 years into the saga yet. OTOH Creo is nowhere near his planned expertise, and Mentem is not top of the list either. It is not at all obvious that he should bother.
Bringing negatives up to 0 or +1 would be by far the most common usage, even if higher level rituals are available. The cost are far lower and you don't have to be a specialist (or 150 year old generalist archmage ). Most Magi would really only be interested in Int +5 and Sta +5. Even then the high cost when +3 is "good enough" would limit the amount who do.
The cost is not really the issue in our saga, not as far as one favoured characteristic is concerned, anyway. Vis is rather abundant, though not quite to the point where we could consider upping every characteristic to the limit in the foreseeable future.
My saga is long and Vis is not an issue. We could all be Str +1, Dex +3, Qik +3, all others +5. No one is close to that. Mostly it was fix the negatives and Int/Sta +3, with a few of us at Int and/or Sta +5.
My character is the only one capable (+64 and +61) of casting both the Mentem and Corpus level 60 rituals powerful enough to get +5s (Serfs Parma, don't know recent XP spends or if they could do it from +Aura, AL, and Philosophiae). Of course as a generalist my highest TeFo is +65, compared to the over +90 plus mMF/MMF that at least two can do in their best TeFo.
EDIT: A post that made me pull up my character sheet that wasn't PBP.
The problem that I play a multi-table game (4-5 covenants each meeting on a different day) who periodical meet up for Tribunal and the STs have approved an interpretation that suggests that enhancement rituals can be cast with target Circle and Duration momentary.
This makes it very worthwhile learning very high levels of the Intelligence and Presence enhancing rituals. When you split the cost of a ritual between 5-6 people and you only need to cast it 2-3 times, the risks and costs get extremely affordable. So we have some real monsters.
We initially were allowing Circle but realized how abusive it would get during the first "in game" casting. We looked at "Targets & Creo" (page 113) and decided Target Individual or Group. You can't really create a circle full of "better body".
You reduce the cost, but hardly the risk. It is good though; a multi-botch with 5-6 people in the circle has some potential. I hope SG is conscious of his responsibility to take advantage of the full potential. It is really unfortunate with the erratum ruling about relaxed mastered rituals.
There would be more victims to each botch, so the expected number of botch victims is constant.
You have a point in that the caster gains fewer warping points on average, but then the severity of the botch is not necessarily linear in the number of victims. It all depends on the imagination that @OneShot alludes to.
Self publishing for Vis is not really an effective process. You (or even better your Covenant) needs to setup a group of trained scribes to copy text. Otherwise you will spend all your seasons copying text instead of becoming a more powerful Magus.
Of course there is lots of material in published books as well as this forum on doing that (including my own Covenant's Worth of Enchanted Items thread).
True. Mostly we do it to get more books in our saga. Income from straight sales is pretty low and we actually have a back catalog. Getting things off the ground from near nothing will not show much return for a while.