I can imagine it working in the sense that faeries have minds, but when we roleplay minds they tend to be antropomorphic, and that is not supposed to work, possibly because the human mind as we understand it is coupled with a soul, and a mind elemental cannot have one. Unfortunately, I cannot quite imagine what a soulless mind (or a mindless soul) would be, and that creates some problems to the roleplay.
The fact that we struggle to define what could be a mind elemental might gives us a clue in itself.
When a mage is using a Creo spell, he draws from the Realm of Form, where what he is creating exists - the mage can name the thing and can define it with words.
If we can't define, can't describe it, then maybe, it does not exist and thus is not possible to create.
If one says a mind elemental is a collection of memory (for example), then it is specifically a elemental of memory and not just a mind elemental. If it is an emotion elemental, then it is an elemental of anger or lust (these sounds clearly like some demonic form) or calmness.
So, I would suggest that an undefined or generic mind elemental does not exist because it cannot be defined.
To keep going on this philosophical trend, would the creation of something that does not exist and never existed (thus no description, no definition of it ever existed), would such creation not infringe on God creation power and would it be a sin ? would it attract Dominion awareness ?
Artistic creation - even if it is always original - is different in the sense that no matter how beautiful or horrible it is, it draws from something existing to make it "more something" (beautiful, attractive, revolting, etc...).
Elementals have a fairly precise definition in Ars Magica, and they are not spirits. They are animated chunks of pure, unworked, matter.
There are also elemental spirits which are spirits of discrete pieces of matter being mostly composed of one element. Thus you can have an elemental spirit of a campfire, or an elemental spirit of a breeze, and so on.
Spirits of memory, or spirits of emotions, and similar also exists, just as there are spirits of animals or plants, but they have nothing to do with elementals.
Spirits of a mind can also exist. The most common variant of those would be ghosts.
When I suggested a "mind elemental" my point was that there are solid guidelines for the creation of a creature with an arbitrary amount of might, and that those could be adapted in a similar way. I'm in no way suggesting that every spirit be treated as such. What I'm saying is that, from a purely mechanic point of view, we have where to go from.
I agree with Ezzelino that there's no evidece that the creation of a spirit (if possible) should be CrMe(Vi).
But is it within reason that some spirits could, in theory, be created by CrMe(Vi)? Yes. If spirits (something classified as a spirit under Ars rules) can be created, it is possible that CrMe(Vi) is a way to do it. It's not certain, however.
Of note, I'd say CrAn can create animal, and CrAn(Vi) magical animals. But CrMe would go in the direction of creating minds, which isn't really a thing. Looking at it the other way: take the magic out of a spirit, what remains? There's your form.
So by that logic, I'd actually say that if you want to create a magical spirit of water you want a CrAq(Vi) spell, a magic spirit of the echo, a CrIm(Vi), and so on. Or maybe, CrVi(Form). Vim is as much formless and without substance as Mentem, and the putative spirit being created with Vim doesn't necessarily stop you from giving it solidity by using Mentem.
But, within my view, the creation of a spirit is not possible through a direct magic act. One can use magic to facilitate conditions in which a spirit would form or be attracted (for example, repeatedly casting a CrIg spell on a certain place might make it easier for a spirit of the flame to appear), but there is (again, in my view) generally no Cr[Fo] spell that can actually bring an spirit into existance. At least, not in a controllabe way. If you want, for example, a Spirit of the Lake to form, all you can do is to build an artificial lake within a magic aura, perhaps cast a few CrVi spells to taint the water... and then, hope for the best.
"May I interest you in a mind elemental instead? Pure thought or emotion given basic awareness and a semblance of life... but still something made? Isn't everything made, in a way?" - Vermonia, the Unhinged Criamon.