I'll take a shot at a first response to your post.........
First, why would you want to changes hoses? If you are going the DIR route (long hose primary, bungeed secondary) then get a DIR compatible reg.......
FWIW, I just sold a swiveled Oceanic Delta 4 reg, the swivel was nice, made the reg very comfortable..........
If cold/dirty water diving is not in the cards for you, then you don't need the an environmentally sealed reg, it doesn't hurt but it may be overkill for your diving.......
Never used an Areis Ion so I can't comment, lots of buddies use Zeagle stuff and love it, is the Flathead VII worth it...........only you can decide........
I guess my position is that many folks get caught up in the gear side of diving, if you need the best (because that is the type of diving you do) then by all means spend the money.........but if your dive profile is warm ocean recreational diving then a basic reg will be more than adequate..............
Remember to look at ease of servicing (your LDS) and cost of servicing, over the long haul those far outweigh the initial cost of the reg.........
I have stated before, that for warm ocean recreational diving, I'm a big fan on the AquaLung Titan................which my son dives.............
My darling bride dives a ScubaPro MK25/S550 and loves it..........
Oh and back to my first question, if you are going DIR then SP MK25/S600 all the way, for the hose routing..........
Hope this help.................M