A Question: how much should ship characteristics be constrained by date?

I ask the question about whether a high-level ship design program should restrict characteristics by date. I think that political considerations could reasonably be waived, if in an alternate world situation where you were designing your own ships and building program, you could possibly specify a ship in 1905 that had 8-20in guns and 15in armor. Reasonably, the guns could be 20in/35 or 40 caliber, and the size would be less. The look would be transitional between pre-dreadnought and dreadnought. The size would still be large, but there could be restrictions against using triple turrets. I'm choosing an extreme case. More normally, you might restrict ships to being under 20,000 tons and to 12in/45 guns at the upper end. You could also restrict SHP/ton of machinery to 10.0, as was the case for British battleships up until 1912. Battlecruisers had better powerplants than that, but only marginally. So, that is the question: by year, what should be premitted with respect to ship characteristics?