Would something like this work just for night time?? I only have 4 ducks that’ll use it.
Would probably have to help them in and out?? I don’t know...
I wouldn't recommend it because the ramp will have to be either quite steep or very long, and if you are already having problems getting them to sleep in a shelter at night, you don't want to make th process more unpleasant for them.
At our old house, the duck was low enough that until the deep litter bedding starting getting high, the ducks didn't need a ramp and even after, a short low one was enough. Now that we have moved to a farm and have more critters, we have several campers we've turned into coops, including one that the ducks sleep in.
Because of this, we made a set of stairs out of cement blocks for the poultry, including ducks, to use to get up and down into the coop. We didn't think this would be a problem for the ducks because they had used cement block steps before, albeit shorter ones.
Here's a pic:
Th ducks do this sort of rallying jump-fly up the steps every night, and it looks like it takes some effort. In th mornings, they either trip down the steps, jump, or jump-fly down them (depending on their grace and dexterity, some use gravity more than others

)
The camper-coops (hopefully) will be fairly temporary and when we design th next duck structure, it will be as close to the ground as possible because while the ducks can manage steps etc, they don't seem to prefer it. This is th experience I've had with my ducks, others may have had more successful experiences with their ducks using steps and ramps.