Would it be feasible/balanced to allow players to slot and cast a companions ultimate themselves without the companion present? It'd only be accessible if we have their keepsake. Perhaps that ultimate meter would still build up separately than our own, so it's an extra ability that can be cast just every once in awhile.
The whole reason I ask is it just seems fun having that extra ability on the bar, but there are times when having a companion out is not practical. Their ultimates seem to be very tame and are more like standard player abilities, so it doesn't sound too unbalanced to me. But I don't know all the minutiae as some folks do.