All depends on what reason you're doing it for really,... i agree that if the OP is doing it (partly) because he wants to disassociate a shoddy brand image by changing the badges... that to me does seem a little lame (in my opinion).
However, let's say (for example), that i love Vauxhall Corsa's, Astra's, Vectra's etc, and let's also imagine that i own 1 of those cars (i don't btw),.. But i really hate the Griffin logo (which i do, as it happens), I would actually swap the badges over to Opel, why?... well because i find the badge more aesthetically pleasing (prefer the simplicity compared to the griffin design)...
So, basically i'd be doing it for myself... Not to fool anybody, Not because i'm embarrassed about the badge, Not because i think in some way it's more exotic because it's a foreign badge..., screw what anybody else thinks, as i'm not actually doing it for them.. i'd be doing it because i like the other badge design more.
So if someone is doing it for that kind of reason, i really don't see it as being lame, or pointless for that matter.