Doing them Sous Vide will work but seems over kill when tey can be done just as well on a hob, with good control and stirring. Or use a thermomix or the new kenwood if you want to do custards etc, with no attention they are perfect for that.
Far from being overkill, I find it easier to do a custard (defined broadly) by the SV method rather than in the traditional ways on the stove top or in the oven. Wouldn't it be overkill to purchase a thermomix or a new kenwood for this when a SV set up does the job just fine?
May I add that SV more generally is not unnecessary, not overkill, not more than is needed to do the job for the simple reason that it is often the best way to do the job.
I sv'd custard once for ice cream, and it was the best batch of ice cream I've ever made. Only complaint is how the bag fills with air unless you have a chamber vacuum...what would be handy are bags with one way valves so the air can escape, but I think that'd be overkill