So many replies, I did not expect that! Thank you all for your interest and contributions. I'll get back to the OP, regarding a combination of MuVi and ReVi, instead of spont Mu(Cr,Pe)Vi.
First off, I aknowledge that powerful Touch/Mom/Ind spells are not available to such a caster. OTOH, casting totals should be boosted by a Magic Aura at most times, and that boost helps with that, if only with a single magnitude. I also believe I may have emphasized too much the specialty, and believe the Vim "Specialist" should also study the other Arts, albeit less than Vim.
As for the notion that this is a strategy that requires many years of experience, I believe that is not the case at all. 1) Only a few formulaic spells are needed; and 2) They do not need to be that high level.
All that is needed are a) Intangible Tunnel-like (IT) effects; b) Maintaining the Demanding Spell (MtDS); and c) MuVi spells.
Let's see how these spells work with low magnitudes:
a) ITs are usually cast with r: arc, d: conc, allowing for same-level spells to be cast through it. A level 5 regular tunnel is opened, or a level 5 tunnel with r: sight, in case there's no arcane connection. IT must penetrate, and level 5 should be easy. MtDS should be used afterwards. With that, another level 5 IT can be cast, but with r: Touch, and d: Mom. A MuVi spell that boosts duration from Mom to Conc should be cast in tandem, and another MtDS to maintain the resulting IT. With a level 5 IT, up to level 25 spells can be cast with r: Touch and actually reach Sight or Arc, which would be level 35 or 40 spells on their own. For every magnitude added to the IT effect, another magnitude can be added to the spells cast through it. Its utility with formulaic spells tops off at level 30, as that would allow a level 50 touch spell to be cast.
b) It takes a modified level 15 MtDS to maintain concentration for up to Moon duration on the tunnel. It does not need to penetrate, so it is not capping the maga's power. It also adds another magnitude to the effect alongside a magnitude increase to the spell level. The utility of this spell tops off at level 40, when it can maintain level 30 ITs for d: Moon. It could theoricatilly be used as a level 50 spell to maintain level 40 spells for d: Moon, or level 45 spells for d: Sun.
c) MuVi spells are able to boost (magnitude-1) spells with r: Touch and d: Conc by a single magnitude, or (magnitude-1)/2 spells by two magnitudes. To target level 25 spells, which were the original IT cap estabilished in "a", MuVi spells of level 30 can be used to boost a single magnitude. Again, it does not need to penetrate. This can be used to target a Room where the individual is present, increase penetration by 5, or increase duration from Mom to Conc, allowing another MtDS to extend it for Sun/Moon. In this case, a level 40 MtDS would be useful. If the inteded target is Group, a level 20 spell can be cast through the IT and boosted by a level 50 MuVi.
Putting it all together:
3 ReVi @ level 5 IT effects (need to penetrate);
+MtDS @ level 40 (don't need to penetrate);
+3 MuVi @ level 30 (don't need to penetrate);
= Level 25 r: Touch, D: Mom turned into R: Arc, D: Moon (effective level 55) or D: Mom +5 Penetration (effective 45), or D: Mom, T: Room (effective 45), all cast in a Magic Aura, perhaps with Wizard's Communion (it's MuVi after all!)
Pulling off ReVi 40, MuVi 30 and generic TeFo 25 at first may be tough, but they all scale linearly when it comes to magnitude, so it's easy to scale it down. To cast TeFo X (which might need to penetrate), you need MuVi X + 5, and ReVi X + 15, neither of which need to penetrate. Maybe it starts off as ReVi 35, MuVi 25, TeFo 20, which means level 15 guidelines + 1 Touch. If you're having trouble with penetration, a TeFo level 5 guideline + 1 Touch can have its penetration boosted by 10 with a MuVi 35. Having some sort of Vim specialization is needed, but not that much.
I'm considering the MuVi formulaic spells can either:
Increase d: Mom to Conc specifically (instead of increasing duration by 1 step), and can target any Form;
Increase t: Ind to Room specifically and can target any Form;
Increase penetration by +5/+10 and can target any Form.
Thanks again for joining in the discussion!