There's no two ways to put it, the Four Years War has seriously diminished Starfleet's active roster. While much of the Excalibur-class remains active and potent, as are more than half the Kea-class ships that went into the conflict, there has been major attrition for less survivable starships. Fortunately the Archer-class represents a major logistical capability that is staunching the bleed of lingering capability losses towards the border, which has provided some breathing room to conceive a more lasting solution than emergency crash builds of older designs. While the Saladin and Selachii-classes were primarily combatants, the Newton was providing a useful response and utility function that the slower (and more logistically valuable) Archers are now having to cover.
More pertinently in strategic terms, however, the Newton's size and quality tactical systems made it the cruiser that made up the 'bulk' of fleet deployments during the war. Their ability to provide a stable firing position while other fleet elements maneuvered around or through their formations represent a key element of Federation fleet doctrine. Put simply, they need a replacement. To that end there are two competing ideas for how to accomplish this, and while Klingon debris is accelerating warp coil and hull metallurgy development, advancements are not expected to mature for some time yet. So you have to do it with the technology you have available today.
The first proposal is for a midweight generalist. The hope is that Project Miranda will produce a starship with a reduction in non-vital capabilities in exchange for a reasonably costed and capable generalist able to take up missions as required. As an in-territory vessel with only basic scientific facilities, the freed space could be utilised for tactical, engineering, and utility concerns. The main question would be what non-auxiliary areas would be sacrificed to drive the costs down.
The second proposal is for the other end of the scale. Project Federation envisions a cruiser more along the lines of the Kea-class, using a higher mass than other contemporary starships to produce powerful defense fields and a depth of capability in vital areas of interest. This idea of a line cruiser would then be able to weather any conflict it takes part in, acting as a lynchpin for a small task force or the main force of battle in a larger engagement.
[ ] Project Miranda (Midweight Generalist)
[ ] Project Federation (Heavy Line Cruiser)
Two Hour Moratorium, Please