Just about the only element of the tactical systems you aren't happy with is having to put the forward torpedo launcher so low in the secondary hull, rendering it potentially vulnerable to hits from the ventral axis as well as forward. But that's the price you pay for cutting out the traditional 'neck' structure that joins the primary and secondary hulls on most Federation starships.
Order -> Spaceframe -> Warp Core/Nacelles -> Tactical -> Scientific -> Internals -> Prototyping -> Certification -> Final Review
[X] Install an Isolinear Chip Computer Core (Prototype)
Isolinear chips are an interesting concept less for the speed increase they offer over standard doutronics and more for their rapidly reprogrammable architecture. Some very clever people have created a standardised system that allows pulling the tray and inserting new chips or rearranging existing ones to alter running programs or reconfigure processing flows. The speed alone would have been more than sufficient to justify rolling the technology out, but given the advantages of the chip system you expect it will be a while before a superior system comes along to displace it. The Centaur will be the first starship trialling the technology, and there are a lot of very interested scientists over at the Daystrom Institute who will be paying careful attention.
With the bone and sinew of the starship effectively complete, the much simpler affair of managing the internal space presents itself. Savings have been made in several areas thanks to prior design decisions. The Excelsior saucer itself has ample crew spaces, of course, and keeping the standard armament rather than plugging in the new phaser array technology has preserved that advantage. The new isolinear computer core is actually slightly smaller than its doutronic counterparts, so that's a saving in addition to the science labs you didn't have to plan for. The engineering spaces were able to accommodate a standard cargo bay as well thanks to the prototype nacelles, which is one less to put into the saucer section. They always want more cargo bays.
All told, you think you freed up seven modules-worth of space. Add in that the Centaur has a predicted crew complement of 200 versus the Excelsior's 450, most of whom were quartered in the saucer section, and that's another five modules, for a total of twelve. Of course the design as it stands is merely acceptable, and that empty space can be used to improve the capabilities of the ship. Given that it's entirely possible you will have space left over after allocating the remaining areas, it seems a sensible rule to mark left-over spaces for general storage, crew recreation, and expansion for new components in a future retrofit.
To help make the decision you draw up an estimated capability chart for the ship as it stands, assuming all the prototype technology performs as promised.
Project Centaur:
Ease of Maintenance: B
Ease of Manufacture: B
Tactical Score: B
Scientific Score: C
Comfort Score: C
Modules Available: 12
Cargo Bays
Small Cargo Bay: -1 Module
Standard Cargo Bay: -2 Modules
Large Cargo Bay: -4 Modules
Crew Lodgings
Officer Small Rooms: +2 Modules
Enlisted Bunks: Standard
Enlisted Communal Rooms: -4 Modules
Enlisted Personal Rooms: -8 Modules
Project Centaur
Goal: Produce a medium-range cruiser with robust tactical systems and high warp sprint factor. Design must be capable of basic collection and analysis of scientific samples.
Minimum Tactical Score: B
Minimum Scientific Score: C
Constellation-class Light Cruiser [2282]
Ease of Maintenance: C
Ease of Manufacture: A
Tactical Score: B
Scientific Score: D
Comfort Score: D
Final Score: 44/100 [Marginal]
[One Production Run of Twelve Ships - San Francisco Fleet Yards, 2282-2287]
Excelsior-class Heavy Cruiser [2285]
Ease of Maintenance: A
Ease of Manufacture: B
Tactical Score: S
Scientific Score: A
Comfort Score: B
Final Score: 76/100 [Excellent]
[Nine Production Runs - All Fleet Yards, 2290-2335+]
Okay good news we hit the minimums, and we probably can bump up science with right picks, that and comfort. At the same time we do want some cargo space
12 modules used, 3 on cargo, 3 on improving science, 2 on a better sickbay for science and crew well being and 4 on better enlisted rooms (the highest end option just uses up too many modules to fit the science labs and sickbays)
[x] Plan Multirole
-[x] Small Cargo Bay
-[x] Standard Cargo Bay
-[x] Multidisciplinary Science Labs
-[x] Advanced Sickbay
-[x] Enlisted Communal Rooms
Cargo bays for samples and supplies, science labs to analyze things, advanced sickbay to deal with both peacetime and combat related injuries and illnesses, and communal rooms to give a bit more comfort to the crew.
Constellation-class Light Cruiser [2282]
Ease of Maintenance: C
Ease of Manufacture: A
Tactical Score: B
Scientific Score: D
Comfort Score: D
Final Score: 44/100 [Marginal]
Well, the ship's fit for purpose. Just about, but at least we shouldn't be considering this an outright failure. I think we should outfit it with something like this:
[X] Plan Multirole
I'm not sure if we can install two cargo bays, TBH, but if we can't I'm happy to leave the slot bare. We know extra module slots aren't wasted, after all, they're just assigned generically. On the whole, though, this plan is good for a medium-range patrol cruiser, which this is. Enough crew comforts and supplies to be happy to do patrolling, not so much that you'd think it's an Explorer, a Sickbay is generally useful, and since Scientific is a requirement even if a low one getting that up should help us sell the thing to Starfleet Command for mass production.
The engineering spaces were able to accommodate a standard cargo bay as well thanks to the prototype nacelles, which is one less to put into the saucer section. They always want more cargo bays.
[X] Plan Cautious Multirole
-[X] Large Cargo Bay -4
-[X] Advanced Sickbay -2
-[X] Enlisted Communal Rooms -4
With two sets of experimental systems, and an old set of armaments, I think there is very likely to be a refit in this ship's future if it works well and I think this plan will work well to accommodate that. The science labs aren't necessary to meet the design specifications and may add cost and crew to the ship, so I think that spending more space on an oversized cargo bay and leaving 2 modules free for miscellaneous uses is probably a cheaper and still valuable way to use the space, which can be easily reconfigured in the future.
I don't see which scores some of the components are meant to contribute to. Personal rooms and maybe advanced sickbay could contribute to comfort and labs could contribute to science but are there any ways to raise maintenance, manufacturing or tactical at this point? Transporters perhaps?