The after-action reports from the Battle of Denobula make one thing painfully clear - the Stingray is out of its depth. This is understandable, certainly: the poor thing was designed to be an in-system patrol boat, or at most an anti-piracy patroller. Nobody at the bureau considered the possibility that it would be serving in a wartime capacity even remotely seriously. War with who? Before the Stingray was phased out? Not likely.
But it's happening, and the reality is that for cost it is still more effective than the NX-class, simply because you need raw numbers to spread hostile fire. But when it takes two Stingrays to be comfortable with taking on a Romulan warbird and you're coming up against force concentrations that equal or exceed your own, something has to give. The order comes down from on high with a simple directive: give Starfleet a replacement for the Stingray, preferably as cheap but definitely more effective.
Easier said than done. The new deflectors are three decks high and even with Vulcan help the first United Earth manufactured shield emitters are several years away. There is no reality where you create a starship that can go toe-to-toe with a Romulan warbird for anything like the cost recommendations you're being given. So you're going to have to make some hard decisions right out the gate.
Main hull first. Arrowhead configuration would give you plenty of space for engines, opening the possibility for a hyper-manoeuvrable vessel with a concentrated armament that is nonetheless capable of staying on target. Problem: with the new deflectors you won't have any forward torpedo tubes unless you can undersling the deflector dish, and even then a single tube will be all you'll get. There might be some way to get a vertical nacelle configuration that alleviates some of the problems, but that would be experimental work.
Possibility two: half saucer. You might be able to get away with the deflector in-line with the hull, but having to mount the nacelles port and starboard instead of from a midline truss would mean occupying substantial internal space with the warp engine and transfer conduits. Optionally a secondary hull would solve the deflector and nacelle problems, but increase mass. Might be worth it for greater tactical output and staying power, but it certainly won't be as cheap or agile with the nacelles and secondary hull restricting engine placements.
[ ] Arrowhead. Aim for a cheap light cruiser. (Industry: 2)
[ ] Half-saucer. Aim for a capable medium cruiser. (Industry: 4)
Two Hour Moratorium, Please.