Using non-compliant wheels could mean possible disqualification. Continuing to do so could ultimately result in loss of competition privileges.*
Now, that said, you could possibly get away with it running regional events locally, as that kind of stuff is rarely checked (but the risk is certainly not zero). And all it would take is upsetting one competitor for them to toss a protest.
But you should completely erase from your mind any chance of getting away with it at "moar importanter" events such as Super Tours and the Runoffs. It will eventually get caught and you will be sanctioned.
There's nothing wrong with properly-done eccentric spacers and wheels studs. In reality, all you're doing is extending the hub face, which is exactly what a wider offset wheel does. Drill, tap, countersink, and bolt the spacers to the wheels if it makes you feel better.
And note that the wheel size is "maximum" so you can actually run smaller if you prefer.
*Technical infractions do not carry points on a competition license. However, continuing to ignore the technical regs could result in a chief steward citing you for "failure to follow officials' direction" and/or "unsportsmanlike behavior". And you can bet that trying it more than once will result in word getting out and your car getting scrutinized every time you showed up.
