I don't recommend it, but I've been in a situation exactly like this with a client. You may experience some disparity in client tracking/traffic analytics data between the two dashboards and troubleshooting will be a bit harder, but it will work.
You are also right in that certain things like group policies may need to be created twice.
I strongly recommend crunching the numbers. I'm not familiar with Spectrum's pricing but the math doesn't usually math on these things, but some operations just like doing OpEx vs CapEx even if it's more in the long run.
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