Which it is
No it isn't. The linksys router is
not designed to protect network equipment outside it's LAN segment, and so the solution as proposed would not be safe for the shop network.
So tell the OP
But the OP is not the one belligerently insisting upon something that is clearly incorrect. You are. I am rather hoping you will learn something about how networking equipment actually works, instead of how you seem to believe it ought to work.
If you believe that, take it up with Cisco. Explain to them the problems you have manufactured and see if they can figure out a way round them. I don't represent Cisco
I imagine Cisco's response would be something along the lines of "this method of operation is not supported" or possibly "this product is not designed to protect the WAN segment" or some other such phrase which would confirm that the linksys router is not designed to work in the manor you seem to want to believe it is designed to work.
On the contrary, it would just continue the situation in this entire thread where you all make outrageous claims without backing them up and I have to drag the reasons out of you all.
Several people have made it perfectly clear to everyone apart from, apparently, you that the linksys router would not be suitable in the set up described in the OP.
I have seen no evidence of you having to "drag" anything out of anyone.
I have seen you, however, sidestep several points, misrepresent issues raised, bring irrelevant distractions into the conversation, and generally refuse to acknowledge any possible fallibility on your part. Oh yes, and not to forget completely refusing to respond to some of the points raised against you.