I got the chance to install a new Cisco ISR 4431 today, and the best surprise (besides the hugely upgraded throughput) is that the onboard router interfaces now support LACP! Before, you had to resort to getting a switch HWIC module, or just using “mode on” channel-groups. Since the 4431 has four gig interfaces, you can use LACP for two WAN interfaces, and use LACP for two LAN interfaces using the command “channel-group 1 mode active”.
#show lacp internal
#show lacp neighbor