There isn't any way to do what you are asking in the base UI. What you would have to do is put your 2-handed weapon, both one handed weapons and Wild attack in quick slots. Lets say:

1) Key '1' is assigned to main hand one handed weapon
2) Key '2'' is assigned to off hand one handed weapon
3) Key '3' is assigned to Wild Attack
4) Key '4' is assigned to 2-handed weapon.

You have to press 123 to do your Wild attack. Press 4 to switch back to your 2-handed weapon. If you have programmable keyboard that can send multiple key strokes you can then program something like F20 to send 123 to the game when you press F20.

There may be some Lua plugins that can support this kind of functionality. Look for a gear changer plugin.

Notes:

a) Some people consider changing gear in combat an exploit. There are requests that Turbine put in a delay timer when attempting to swap items in combat.

b) Sending 123 via a keyboard does not always work. The server and client is performing poorly due to heavy load, lost packets or other issues. Your 123 could easily turn into 13 or 23 or 12. Which result in a Wild Attack with a one handed weapon and a waving around a fist for inferior damage. Or your character standing around dual wielding. Now what boss?