MDA is the MDA, you cannot bust this surface. When on final, you have to include momentary descent, whatever that is for your ac and conditions. It is not necessary 50 feet, the operator is required to calculate this based on the conditions.
Granted, you can't go below MDA. Algol asked a question about adding 50ft to the MDA for a
circling approach. What's to stop you descending to MDA (but not below!), then flying level at MDA to the missed approach point, then executing a missed approach if not visual? What would be the point of adding 50ft?
If you are on final, and decide to go missed, between the decision to do this, change config, and the ability of the aircraft to actually go from approach to climb, lets say that you decide at DA to go missed, and change config?I think most would find that the 50 foot descent is not actually obtainable.
That hasn't been a problem in any airline aircraft I've ever flown! The PF raises the nose, increases thrust and calls for go-around flaps. The aircraft is already climbing away before the configuration changes.