Geoserver 2.12.3 (olders have been tested too with same observations)
A first layer is created to load a shape projected in 27572
A second one is created to load a raster projected in 2154
An agregation is created to mix these two layers, projected in 27572.
The shape is not well placed on the raster, not very far but not good.
If I compare the definition of the projection and the projection on https://epsg.io/, I can see that there is some differences (parameters TOWGS84 is missing, some values are differents…).
I can then use epsg_overrides.properties to define the projection given in epsg.io.
Unfortunately, the result is worst.
After further try, I mixed the native parameters of 27572 known in GeoServer and official parameters given on epsg.io and obtain something good :
I hope it could help.