I want to clarify something. Just because something is a model swap does not mean it inherently breaks the rules of the site. Yes model swaps can be easy to do but something being easy to do is not against the rules.
Now model swaps can often result in glitchy and realistically unusable mods, in those cases it is still fine to flag that content as any mod that is basically unusable shouldn't be submitted to the site. This rule applies to pretty much anything, if you submit something in a glitchy and/or broken state, you should not be submitting* it to begin with. However if a model swap is submitted and functions fine and is not glitchy, then you should not flag it. If you disagree with this, by all means let us know, I'm simply informing you of the current rules.
*(expect WiPs which is a good place to submit something that is currently unfinished but you are working on)
On this topic, I would like to talk about flags. Flags are not a "I don't want this content on GameBanana" button, flags should only be used if a submission breaks the site rules. A modification being bad, is not alone a reason to flag a submission. Please consider that the submitter might be young and/or new to modding and getting a flood of hate is enough to put someone off the site for good. By all means point out what is wrong, but please try to keep feedback constructive, not just bashing.