Can I use scapy to forge custom packets on WPA2 network? Can I even pack the IEEE 802.11 headers?
There are several dot11 classes that are declared to help with low network layers. However, based on their less than adequate documentation that WEP is the only secure protocol that is somewhat supported. Scapy's manual shows some WiFi sniffing, but doesn't really delve too much into Wireless communication.
All-in-all you'd probably have to hack together a mixed solution of raw data, and some of their classes to do what you want. Not impossible, but not as easy as spoofing other protocols with Scapy.