I think a variation of the current ammo-mechanic would work great with the conjuring weapons.
My suggestion would look like this:
The utility-skill itself has up to two charges.
If you're not holding any conjure weapon, using the skill will place one in your hands.
With the weapon equipped, the utility-skill changes into a version which allows you to place the second weapon on the ground.
Once you let go of your weapon, the utility-skill changes back.
For elementalists this means more control over your conjured weapons, especially if they're a part of your rotation. For everyone else this means less weapons which clutter the ground.