Can I install lower-rated fixture sockets to meet the rated current threshold for dimmer switches?
You'll want a pro to help you with dimming.  Dimming LEDs is complicated -- well that's not true, native LEDs dim far better than any other type.  The problem is most screw-in LED bulbs are designed to "play well" with dimmers which also must play well with incandescent... and this results in extreme inelegance.  

All that to say, if you use screw-in LED "bulb" replacements, you may be disappointed with the dimming.  However at the commercial / industrial level with fixed-LED (non-bulb) luminaires, there is much better tech, such as digital or 0-10V dimming controls, that really use LEDs up to their potential.  Don't be afraid of non-removable bulbs, LED emitters will outlive the building.  

If you have plenty of extra panel space, I would not worry about reducing the number of circuits, because it costs money to do so, and why mess with a working system.  Remember if you have an Edison socket, some dimbulb  could screw in a 100W incandescent, then you must provision for that load on both the power supply and the dimmers/controllers.  

If you must use sockets, use candelabra, as you can provison those For 40W as it's difficult to get incandescents above 40W. Strong LEDs are readily available at sane prices.  Don't waste your time with GU24 or any of the odd-duck sockets, the "bulbs" cost a fortune and the sockets will be gone soon.