Being a complete layman I'm interested in whether it is a restriction of the method or some fundamental requirement. Is it in principle possible to replace broken mtDNAs of a mother with mtDNAs of a father, which are mtDNAs of his mother?
It looks like the current techniques might better be described as "nuclear donation". You take an ovum with healthy mitochondria, remove the nucleus, and insert the desired nucleus from the woman with bad mitochrondria. So yes, currently, the mitochonrdria have to come from an ovum, and therefore a woman.