Have a look at the attached picture. It shows the process of building a trench - note the fully constructed section with the gabions on the defenders side, crowned with fascines and the spill on the fortress side.
This would make a nice set of resin fieldworks -- fairly long completed sections which can be assembled into the trenches and "head of sap" sections. The shield on wheels can be kitbashed from a limber. You already have the sappers, although a kneeling chap with a shovel would be nice for the head of the sap.
So, two packs, one with long straight sections, and the other with a sap head, kneeling sapper and rolling shield.
Because the works were always straight sections facing the enemy there is no need for corners, or for full fixed-width trenches in the WWI style.
There are no real competitors in 10mm. Langton makes some very nice ACW works, but they are wood-plank lined rather than gabions and have header logs in the ACW style -- they are firing positions not siege works. WWI/II trenches are easy enough to find, but are quite different animals defending against a different sort of attack.
I have filed this under 18th Century, but they are good from the 17th (at the latest) through to at least the Crimean War.
The trenches would probably do for 1870 1871 siege of Paris too!
I don't think they would become obsolete until the sandbag became cheaper than the gabion.
I'll pop these on the lists!