Namaz e Wahshat is a recommended namaz for all there is no restriction that only Wali has to recite this namaz. Anyone can recite this namaz for any Muslim and Niyyat would be that particular deceased person.
As for as Namaz e Mayyet concern it is a Wajib Kefayee for all Muslims to recite namaz for a Muslim. We should not keep silent while everyone has to recite if he knows what has to recited otherwise he/she has to repeat while Imam is reciting. If anyone does not know he may recite either from phone or paper etc.