I tried searching the suggestion forums but I didnt really see anything pertaining to this, excuse me if its a dupe.
Scenario: My hero's inventory is full with Crushing Claws in one of the slots. My Courier is carrying a Pretender's Crown and the Fortified Bracelet recipe. When I use the Go to Hero/Transfer command on the Courier nothing happens when the Courier reaches my hero.
The only way I know around this problem is to free a slot prior to the Courier reaching my hero. While the Courier is a lot better now than say 2 months ago, the game should be smart enough to combine items without having to free up slots before hand.
They've already allowed you to combine items on the monkey, finnish combining on your hero (full slots, one item from courier or shop). You're talking about having more than 1 item drop onto your hero (6 items already) to combine items I assume.
I normally have my hero drop the single item on the monkey (that has 2/3 of the items) to finnish, and then transfer back. I don't see this as being high priority, but they could look into allowing what you're asking for.
They should allow for more than one item to combine with 1 or more in a heroe's (full) inventory. There are a few item heavy recipes for which this would be nice.
Unfortunately, the vast majority of players don't regularly use couriers (they usually demand use of mine, the cheap bastards).