I would not recommend a spool as a primary reel. You will likely be swimming more than 100-150 ft on several wrecks so you would be better off w/ a primary w/ at least 400' of line. Keeping couple of spools are not a bad idea, but use them for blowing bags or as a safetly reel.
I consider "real" wreck diving to mean deep wrecks and penetration. I agree w/ the BP/W but you should not be relying on a pony in this environment. If this is what you want to do get the training to do it and start diving doubles.
I see where you're coming from and don't necessarily disagree with you.
That said, we're talking PADI recreational diving; "real" wreck diving is specialized and far beyond the scope of recreational wreck diving certs.
For the AOW wreck adventure dive, penetration is not allowed. For the Wreck Diver Specialty course, "...penetration-training dives are to be limited to within the light zone and within 40 m/130 ft from the surface, vertical and horizontal distance included."
As such, I wouldn't worry about having a reel for the AOW dive; this really is a try-out kind of thing, intended to teach certain considerations and, to some degree, reemphasize the importance of further training before penetrating. If going straight on to the specialty course, 125' is plenty.
You may, of course, move on and end up needing more equipment, but I'd get a cheap-o 125', if anything, for now and spend the big bucks on the right equipment, once you have the experience to know what the right equipment for you is.