Good idea...two tenders-in-one!
While many tenders come with a coal load, either a snap-in piece or moulded as part of the tender's body shell, I prefer to remove whichever happens to come with the tender, then rework it so that there's at least some depth to the coal bunker.
That way, I can use "live" (loose) "coal" in the tender. While it's not necesary for operations, if you shoot a series of photos of, f'rinstance, a train during its workday, you can show that as the loco works, its coal supply diminishes.
It's actually easier to depict if you shoot the pictures in reverse sequence, with the coal in the bunker very low, and then add coal as the pictures add-up. The final one might be of the tender being coaled, or of it full, just after being coaled. If you then arrange the pictures in reverse order, the coal pile in the bunker will decrease as the loco works through the day.
Here's a shortened tender, from a Bachmann Consolidation...
...and attached to its locomotive, just out of the shop...
This tender, from an IHC Mogul, was for an oil burner when I first got it, but I shortened it, then added a modelled coal bunker....
...later, I rebuilt it again, increasing the capacity of the cistern, and further modifying the coal bunker...
...and modernised its locomotive, too...
This brass Mogul's tender had an open bunker when I got it...
...but when I modernised the locomotive, I also increased the size of the coal bunker...
While I like Ten Wheelers, these ones, from Bachmann, were a bit too old-looking, even for my late '30s-era layout. The tenders looked too large, too, especially in width....
I both shortened and narrowed the tenders, adding a partial coal bunker......
...with the bunkers fairly shallow due to the weights installed beneath it...
With a few modifications, I had a pair heavier-looking locomotives , with tenders better matching tbe locos with which they were paired...
Wayne