I'd be sticking to a straightforward engine swap. That Skoda above (which looks fantastic, and is probably an engineering marvel) is still showing on the DVLA as 1300cc. I bet there's no mention of it being a completely different set up to its initial "Rear-Engine, Rear Drive" set-up. It may be correctly insured, but if the V5 is wrong, insurers would not be likely to cover it. Plus... road tax fraud...
Maybe there is someone on the theskodaforum.co.uk waxing lyrical over all the minis that are obviously ringers or not in the right tax bracket...
Don't get me wrong, I think it's an epic car. However, I don't like people playing fast and loose with the rules we all have to follow. If that guy lost control and wiped out a Mum and Child on the pavement, the insurance company, press, police, etc would make things very nasty for them. All for the sake of a bit of effort and paying a few more quid. I don't get it.