So for what I'm currently engaged in for creating elemental divine names: First I wrote out the elements in english, then removed letters common to all of them.
This gives F = fire, W = water, and H = earth. Air, interestingly enough has no letter of it's own. Also when compared to german it is the only element word that is drastically different from it's english counterpart, being "luft". I'm still considering ways to remedy this besides using the letter A because I feel if I use one vowel then I may as well use them all as there are, conveniently, five of them. For spirit R seems appropriate as it is the one letter contained in all of them.
Now, for the case of using the vowels. If you amplify the harmonics of your voice starting from the lowest, essentially trying to isolate the Fundamental frequency of the note, and then progress upwards from there to higher and higher harmonics, the sequence I arrived at is UOAEI. What strikes me about this as a side note is that if you go in reverse it sounds like a very sonorous and smouth intonation of IAO. Consider the E transitory between I and A, and the U as simply a double O and that's exactly what you get. Anyway, whether to consider the higher harmonics to be related to fire, and then progress down to the lower and hit earth, or to start from the fundamental and go the other way round has two considerable points swaying me on either side.
The first is the principle seen in cymatics. If you don't know what this is I strongly suggest looking it up as you wont be disappointed. This suggests starting the progression towards manifestation from the lower frequencies (U=fire) as cymatic patterns increase in complexity as you go higher in pitch and this mirrors nicely the progression of division and greater complexity as you move towards concrete manifestation. I should mention that these considerations hinge upon the formula of YHVH in it's elemental sense and progression. The second goes the opposite way based upon the notion that earth is slower and heavy (more inertial) and so the lower frequency fits in well there. Also higher frequencies tend to be associated with higher states of energy. "A" sticks out in this scheme (whichever direction you take it from) as being best associated with spirit as it is most open and contains the fundamental and all of the harmonics fairly evenly represented; moreso than the others which begin to filter either the lower or higher harmonics as you move towards them from the open mouth, flat tongued A.
This vowel system being so closely tied to YHVH and the four worlds formula has raised consideration for using it as a means to denote what level of being is called upon; opening up possibilities for signifying whether something is a god, archangel, angel or elemental. This option needs further consideration and to be weighed against the vowels as being more suited to such a purpose or as elemental signifiers.