.. folk are tending to worry a bit too much about a particular corner of the envelope. It's useful, even necessary, that you should be aware of the concerns .. but it is not necessary to get ulcers about it all.
(a) the takeoff will be (or should be) planned and predicated on meeting all the rule bits for that takeoff, including the consideration that whatever level of flex and/or derate is used is all that is required ... ie unless something dreadful happens, there is no need to increase thrust .. and, indeed, doing so can create problems unless that is something for which you train in the box .. ie you are used to the exercise
(b) the Vmcg/Vmca concern only raises its head for very light takeoffs when the speed schedule is very low and, depending on the aircraft Type, may get down in amongst the Vmcg/Vmca weeds
(c) if the speed schedule is moderately above Vmcg/Vmca then there is no real concern to be had .. although it is much more sensible to advance the throttles slowly if more thrust is your need for some reason on the day
(d) one of the basic concepts underpinning Type Certification is the idea that the throttles are NOT TO BE reset during the takeoff ... so the pilot should NOT increase the thrust setting unless there is some very good reason to do so. I suggest that the reason that it "gives us a bit for mum and the kids" is NOT a good enough reason to complicate the situation at a time when you already are more than busy enough ...