That's pretty much the British equivalent of my beloved LC-1/LC-2/ALICE web gear.

The main shortcoming of civi web gear is that if you're not carrying nice heavy ammo in the front pouches, the canteens and buttpack in the back pull on the suspenders and cause the front to ride up. Also, with my growing beerless beer gut I have to wear the belt lower in front now and the pouches hit my legs when I squat down. The vest solves this.

So, modular of fixed? A fixed vest is probably lighter, stronger and less bulky IF you can find one that has exactly the size/shape/number of pouches you need and you never change. MOLLE looks like a neat idea, but I wonder how well it works in practice? It seems to add a ton of weight and bulk with all the webbing.

I wonder if my wife's sewing machine can handle #69 thread and 1000D Cordura...