Well, as a fan of castlevania, I'd give a few suggestions for making a full base class. First, you might try staggering when they get some of the subweapons, though that may not be needed.
For that matter, you may also look into adding some of the other subweapons that have been used in past games (crystals or bibles seem the most likely candidates).
Also, you may want to give some abilities to enchant their whip/spike chain with the various elemental whips that are common in the games (though only one at a time).
If you want to try borrowing from the Lament of Innocence and Lords of Shadow's which both happen to have more in the way of various moves, you could try adding a whip/spike chain themed maneuver progression (by which I mean only grant them access to thematically appropriate styles using those weapons).
Also seen in those games (and possibly others), is traits that modify how your sub weapons work. In Lament, you have the orbs, while in Lords you have the light and dark magic. Perhaps implementing something like that could be used to help expand out the class (at which point the grand cross would likely become a form of the cross like in lament).
As for some other more mechanical suggestions, The cross boomerang could be done like a holy line breath weapon, to represent it going through enemies. If you also want to show it coming back, you could make that occur the following round (as a second line effect coming back to you).
A double jump ability may make sense, given it is a staple ability in the games (perhaps the ability to make a second jump check at any point within the current jump).
Grand cross seems like it would just be a powerful AoE ability.
Owrtho