So starting actually with Carcharodons, I am thinking this is a poor mans Space Marine Fleet.
Maybe instead of Carcharodons, it is made into a Frontier Space Marine fleet, and I just put the red wake rule in there as an optional upgrade for Carcharodons. This is actually probably what I will do.
SO I am thinking the following
All LD, Captains, rerolls and upgrades the same as other BFG:R SM Fleets.
NO Fortress Monastary
0-2 Battlebarges
-The Nicor (carcharodons only, counts as a venerable BB)
-Venerable Battlebarge (may have 2 unlike other sm)
-Space Marine Battlebarge
0-15 Cruisers
-Space Marine Strike Cruisers (1 per other class of cruiser)
-Vanguard Pattern
-0-6 Crusade Pattern
-0-3 venerable cruisers (IN/Chaos Cruisers or battle/Heavy Cruisers. Must buy a space marine crew.)
Escorts
-The Scrylior (Carcharodons only)
-Nova
-Hunter
-Gladius
FOR Every squadron of Hunter, Nova, or Gladius you must take a Rapid Strike Vessel squadron of at least 3 of:
-Sword
-Firestorm
-Cobra
Reserves may not be taken. Always assumed to have the highest attack rating. Do not require a LD check to disengage. No thunderhawk annihilators.
THE RED WAKE: Carcharodons capital vessels must take The Red Wake for +10 pts. Escorts may also take it for +10 points (optional). May reroll the results of any Hit and Run and receive +3 for Boarding Actions instead of the normal +2 for Space Marines.