On Sistanis webpage it says: «A temporary marriage that is not for the purpose of deriving sexual pleasure is valid. However, the woman cannot stipulate a condition that the man must not derive any sexual pleasure.»

Here it says a Mut’ah where the purpose is NOT to derive sexual pleasure is valid, but does that mean a mut’ah where the purpose would be to derive sexual pleasure is not valid? If one does mut’ah with the intention of having sexual pleasure in order to not sin in other ways (such as zinah or masturbation) would this not also be valid?
-Rather even if the intention of avoiding sin was not there, and one do mut’ah simply to gain sexual pleasure, would that not still be permissible?

What is meant by the fatwa is the validity of the temporary contract if it was made for a purpose other than sexual pleasure, as if the purpose of it was to prohibit the mother contracting with the contracting party. But is it possible to put this condition in the contract, for your wife to tell him about the known dowry within the specified period, provided that he does not enjoy me sexually?
The answer is that it is not correct to set this condition, and the husband has the right to sexual enjoyment if he wanted to.