Accepted. 
Except these effects are fairly low level, and with such dedication to Mentem as you suggest, could probably have been sponted anyway.
Or the spells could've been invented en masse, several to a season.
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Mmmm. Not really. The guidelines are lowish level, but if you start adjusting for R/D/T and complexity, you easily get into the 20s. And remember that DM has two advantages: it allows you to create spontaneously which you could not otherwise have created spontaneously, and it allows you to create spontaneously without fatigue that which you could have otherwise created, but only if fatiguing yourself. Finally, note that it's not trivial to invent spells "en masse", particularly if you do not have lab texts for all of them.
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We're talking about effects similar to Panic of the Trembling Heart or Rising Ire, no? Those are level 15.
Yes, you can make them more complicated, but they are a decent place to start I'd say.
Now, this is obviously very saga dependent, but IME Mentem specialists do have an easy life.
Inventing multiple 3rd magnitude spells might not happen the first decade after Gauntlet, but soon enough there after, surely?
Or was my last Mentem-specialist just riding the easy-train?