I assume you're using gas turbines?
If that's the case you'll need a much bigger exhaust since the Nimitz class has more than 2.5 times the engine power of a Hyuga.
You'll also need to move it forward in order to gain room in the hull for the turbines.
I don't think for a ship of approximately 100,000 tons that it is convenient to use gas turbines as propulsive system. I thought more to a system like steam propulsion like Kennedy aircraft carrier.
CV Yamato (Nimitz) vs
[J.F. Kennedy]:
Displacement: 100,000 tons
[82,655 tons full load]
Length: Overall: 1,092 feet (332.8 m)
[1,052 ft (321 m)]
Waterline: 1,040 feet (317.0 m)
[990 ft (300 m)]
Beam: Overall: 252 ft (76.8 m)
[252 ft (77 m)]
Waterline: 134 ft (40.8 m)
[130 ft (40 m)]
Draft: Maximum navigational: 37 ft (11.3 m)
[36 ft (11 m) maximum]
Limit: 41 ft (12.5 m) [37 ft (11 m) limit]
Propulsion:
[8 Babcock and Wilcox boilers 1200 PSI, 4 steam turbines, 4 shafts, 280,000 shp (210 MW)]
Speed: 31.5 knots (58.3 km/h)