Edges do not support VLANs, and the LANx interfaces are all part of the trusted network. You wouldn't be able to assign separate networks to each LAN interface. You can assign a separate network to the OPT interface though. And you can use the built-in DHCP server for each.
What type of VPN do you want your teleworkers to use? PPTP, IPSEC or SSL? The Edges only support 10 concurrent PPTP tunnels. With everything you're trying to accomplish, I would recommend an X550e, maybe even a X750e, with any business-class wireless access point if you want to offer wireless to your users.
The company I work for is a WatchGuard Authorized Reseller if you are not currently working with one.