I don't think this conversion is worth fussing over. I mean, he hasn't apparently damaged the cabinet in any way that's not reversible, except maybe the control panel itself (easily replaced), and he kept the original theme intact. If the vector monitor on it was dead, and chances are it was, the odds of finding a replacement at a reasonable cost are practically nil. Plus, SI Deluxe isn't exactly rare or high-demand.
Personally, if there's going to be a conversion of a non-generic cabinet, I'd rather it be like this - tasteful and reversible - than painted black with MAME logos on it. That said, I still wouldn't pay $1800 for it...