>>21 You are welcome. :)
>>22Thanks for the information as well as your compliment,
but I'm afraid your Wikipedia link seems to be one for Sanskrit.
According to my little research, the desiderative form for Japanese refers to forms such as the Tai-form, which is preceded by the 連用形(Renyoukei) of a verb, like "してもらい たい", and that can be literally translated as "I want X to do 〜".
http://japan-studies.com/language/grammar/constructions/desiderative.phpAs for the subjunctive form, "もらおう" is categorized here as a contraction of the 未然形(Mizenkei) + う form, as you mention, according to this "Contractions with group 4 verbs":
http://japan-studies.com/language/grammar/constructions/subjunctive.phpHowever, I am neither linguistically trained nor totally assured of the credibility of that website concerning the terminology. They sound confusing to me too when it is mixed up with English grammar.
Please correct me if this is incorrect.