Yes, you can trick the system if you want to. It has been this way for a long time now, so it's nothing new. The problem was that many people used to drive around without uploading their skin, as if it was in some way difficult to use our system. We've made it really easy to use so there's no reason not to do it.
The point of a skin is not so that you can see your car's interesting paint job, while others see a white car. That is not the idea at all. In fact you as the driver can't see much of the skin. So it is about how your car appears to others. I feel silly saying this, it's so obvious!
I realise that there are some people who are intent on driving around with a skin that is a secret known only to them and they don't want anyone else to see it. I don't try to understand the reason for this, as I don't need to. It's pretty obvious that you can upload a plain white skin called XFG_SECRET_SKIN.jpg while your own local version of XFG_SECRET_SKIN.jpg has your top secret design on it. We aren't stopping you doing that. We're not doing a CRC check on the skins. This isn't about law enforcement. It's about encouraging people to use the automatic skin download system we have provided.
What we have stopped, with this system, a long time ago, is the hundreds of people driving around with skins on their cars but too lazy to upload it to LFS World. They just had to log in and look for the upload skin button... problem solved!