Yep, center consoles are limited for diving because space divided in front and behind the console is not as useful as same amount of contiguous deck space (hope that makes sense). Forward space is useful mainly for storage so four divers gearing up on the back deck will tend to feel more crowded than a boat with a helm forward.
One solution is work out a system like Wookie indicated, but diving in shifts slows down the day and limits the number of dives each diver can make (may not be a big deal).
I would love an enclosed cabin but it hasn't happened for me (yet

). Rule #1 for small boat diving is Pick Your Day. Therefore, I only go out when the weather is decent (<10 mph wind, <4 ft swell). No point in having your fillings pounded out of your skull while someone throws cold buckets of water over you LOL. Under good conditions, I am happy with an open cockpit. Luckily, that doesn't restrict diving too much in sunny Southern California (not so sunny today though....)
One of these days I will probably get new Eisenglass made up and do a 3/4 enclosure under the tuna tower. In the meantime, I have a good boat parka, hot soup and snacks, hot shower etc. and limit my diving to good days.
If you are going to be running a heavy load as we divers tend to do, make sure you look into selecting the right prop(s) and trim tabs. They can dramatically improve the performance of a heavy boat. Also try to put more weight forward to get the boat out of the hole and up on plane quicker.
You mentioned cats ... they have a deservedly great reputation for maximizing deck space and for economical performance but I have heard some designs can be a handful in a quartering sea/following sea. I've never driven one but I would recommend a sea trial on a snotty day before you buy.