You can configure "internal" to override if you choose, there is a checkbox on each channel in the setup... however, I wouldn't do this...
First, if you have all sites going into the same suite, you really shouldn't be using UTMs... UTMs are for external campaigns, if you are also using GA using UTMs will cause issues with GA Session tracking... it's preferred to use ITMs or custom parameters for your internal campaigns.
Next, I would set up a special Marketing Channel for your internal campaign (separate from Internal) that overrides if you choose... or don't record this as a Marketing Channel at all, and track your ITMs separately and pull the data directly for this usage.