I have an appliance with 6 gigabit-ports and search for an option to trunk 2 or 3 port for one interface. Since many of today's appliances have more ports than needed, trunking would be a very useful feature.
Back to the first question, this is not as easy as you think...
If you have LAC on two interfaces, now what? It has to go somewhere, and that means LAC on two other interfaces. Now to use that you have to push 2 gig (less overhead) on two different virtual interfaces. (Total 4 gig of traffic) How fast do you think your system buss is in that appliance? There is a reason for Layer 3 Switches... It is because full routing and firewall functions take system power, and to "route" 2-10 gig traffic, you really need switching fabric over a powerful backplane.
So, until we have a new bus standard (by which time 10g nics will be standard) this will not really be possible.