[tl;dr] After considering the total length of benches I might lose a few feet of space in converting to central benches, but it'd be approximately the same. And I didn't take into account that my plants are tall. (catts, bicolors, purpuratas etc) So my original layout might actually be what works for my collection. Think about the plants, don't think about how pretty the benches are.
[Long Story] The gh(s) have 8' walls, 11' at roof beam. and about 9' wide. 2 of them are back to back so about 24' long ( I took the interconnecting walls out a few years after i built them so it'd be one continuous unit} so it's approx the size of a shipping container. twinwall on the sides with an insulated kick wall. and triple wall on the roof. The benches are at about 40" with room underneath for a single level of those plastic shelving units you can get at Home Depot if I need more space. And I have a variety of methods to hang plants too. So I guess that's be a total of 48' of permanent benches with an option for about another 40' if I used all the under bench space. Plus whatever I choose to hang.... At times I put those Home Depot benches on top of the permanent benches if I want the plants to be warmer/brighter in winter. For the most part minsters are under bench only.
I was looking at Bill Thoms gh benches (he has several videos online) and I think Sue Fordyce used a similar design in her home gh. 2 flat benches side by side at standard counter height with a second narrower bench about 18' above that. So I'd still have about 48' of bench plus 24' on the narrow shelf above. Then whatever hangs over the aisles. I'd have to control for plants dripping on each other - I hate plants dripping on each other. When I hang plants they are over the aisles. Anyone taller than me has to duck to walk in the gh, LOL!
Most people I know use flat benches a bit lower than standard counter height. A couple of people I know with central benches have the benches hanging from the rafters so the hoses don't get caught on bench legs. Gold Country Orchids has rolling benches in one of the ghs, and I guess it works well enough as long as it's just him and his workers - not a ton of people trying to access the plants. Yeah, in my gh it'd just be me.
Hmmm...as I write this I'm beginning to think my original design works pretty well for me. Thanks Ray for making me think of total bench space, not just the configuration.
Except the air blowing down/up the gh walls is brutally hot. At times 110f+ whilst the ambient temp away from the walls is more like 85-90, which is why I was thinking of moving the benches away from the walls. Well... I'll think about that. I might have to install roof vents. Something I didn't do in my original design becasue I depended on a swampcooler to blow the hot air out and regulate the temps. I might have to buy another one.