Symmetrically decimating a mesh

Hi guys, so here’s the situation:

I created a mesh (or rather one half) and mirrored it using a modifier in object mode.
Now I want to give the mesh a sort of robotic look. Basically I want to visibly simplify the mesh and later on use the edge-drawings of the uvmap as part of the texture to give the object sort of an assembled pattern (as if all faces were individual pieces of metal).

The issue I’m having is that decimate won’t let me modify the mesh without applying the mirror modifier first. The second issue (if I just go ahead and apply the mirror modifier) is that the decimate modifier does not produce a symmetrical mesh (which would result in more work later, also why would anyone design an asymmetrical looking robot?). Plus I wasn’t particularly satisfied with the results anyway. I remember reading about python scripts flying around that offer new functionality (and some were recommended for simplifying meshes) in stone-old posts.

To sum it up: What are my options here?
And how would you experienced guys do this?

Thanks in advance!

No blend file supplied (why not when you should be doing so for ALL support questions?) so cannot give specific solution.

Testing and it will allow applying a decimate modifier with a mirror modifier (in edit mode). You can also add the decimate modifier above the mirror modifier to then still maintain a symmetrical object

Also look at:
Delete mirror modifier, decimate, add mirror modifier
Apply mirror modifier, decimate, cut in half, add mirror modifier
Apply mirror modifier, decimate, use symmetrize tool to make both halves the same