Your explanation makes as good as no sense to me.
Well... It\'s true that my English is not perfect.. But you are giving arguments, so that\'s fine.
Mana or mental stamina or whatever you want to call it has no direct relation to physical stamina. Physical stamina is the potency of your muscles while mana is magical energy.
Mana has no direct relation to physical stamina, I am agree. For what I called \"mental stamina\", it is true that is not really the same thing but when you are really \"low\" at one of them you can do nothing. Und the current state of developement of PS doesn\'t allow to distinguish each one from the other one. So as a beginning and in order to simplify the first implementation of it, I suggested to only use stamina.
However I do not really see why we need a mana bar, especially right now. Needing mana is yet another thing that currently unbalances whole the mages vs fighters equation. A fighter can keep hitting but a mage can\'t keep casting because he \'ll run out of mana.
That\'s the main point and we are agree.
Ceremony, which is composed by a amount of time, gestures, speech, symbols, objects, material and concentration is a help to the caster and help him to use surrounding mana.
The ceremony use stamina(body stamina can be a little for some movement, more if there is some kind of dance), \"mind stamina\" (concentration), may have blood like symbols, objects or material, and like I say before other symbols, objects or material.
The mage have to choose how he want to cast his spell but there will be bonus/according to the importance of the ceremony.
Experience allow to reduce the importance of the ceremony, and \"it is say that\" very skilled Mage can cast a spell without ceremony or with an impercetible one.
The environnement should give also bonus/malus as you explainded it.
The last thing is that the Mage is able to use his own energy(stamina,hp,age ...) in order to help the casting of the spell. However if the spell is miss-casted, the draw back are worse. This kind of spell is usually called \"dark\" or \"forbidden\".
PS: Feelings and devotion to the god related are also factors.