modern AVLBs may take a couple of minutes to deploy, but I think you will find out that most of the older ones (like the MTU or TMM) take more like 20+ minutes.
Besides, if you feel the need for it, you could certainly use any amphibian- or LC-class unit with 0 speed to figure an already deployed bridge, which you would then use to load and unload units from one side of the river to the other.
Not sure how well it would work exactly (not mentionning how it would look!
), but if that's the kind of things you are specifically looking for, it may be marginally worth a test.