It all looks great to me. The only things that I can add are...
1.) To use something better than ball valves to contol flow. They will work, but will not give much fine tuning and will be hard to set "just right". Gate valves are a much better chioce on the affordable side and actual flow control valves are much better, but get pricey.
2.) Use a dump valve (I used a flow control valve - a gate valve would be OK here too) so that when you are using the wintertime head, you are not pumping the whole load to that one diffuser or choking the pump. If you turn off all the deep diffusers and leave the shallow one wide open...you will shorten the life of that head...if you choke that head down...your pump pressure will skyrocket and you'll shorten the life of the pump. I open the dump valve all the way exhausting the pumps air out to atmosphere, turn off my deep heads, leave the shallow one wide open, and then start shutting the dump valve until I get it to look right. Most of your air is just escaping and you are only getting enough to the one shallow diffuser to make it work at a proper level. The most efficient way to do this is to swap out pumps in the wintertime to one that is sized for just one head, but not necessary if you are OK wasting some energy.
3.) Install a pressure relief valve at the pump just in case something gets plugged up. You don't want your pump pushing against a blocked line and overheating. I bought one from McMaster Carr. It is adjustable from zero tp 20 psi. It always leaks a small amount, but is good insurance. IIRC I set it at 10psi - thereabouts...
48935K25 - Adjustable Pressure- and Vacuum-Relief Valves for Air and Inert Gas, 440C Stainless Steel Seal, 1/4 NPT Male
While I am here, I will throw out what I bought for the pump house cooling fan, intake filter, and gage...
4369K31 Corrosion-Resistant Air-Intake Filter, 1/4 NPT Male, 10 scfm @ 100 PSI Maximum Flow Rate, (note: comes with filter element)
4369K38 2-1/4" High Paper Element for Corrosion-Resistant Air-Intake Filter
9191K32 Equipment-Cooling Fan Kit with Thermostat, 4.69" Square, 100 CFM Airflow, Steel Guard
3845K1 Vibration-Resistant Pressure Gauge with Plastic Case, Dual Scale, 1/4 NPT Male Bottom Connection, 0-30 PSI
Hope this helps!
