Apart from it being illegal
I am then glad to see you know it to be illegal, but surely you are the king of your castle

I have to say I'd stop well short of giving that kind of advice to homeowners, users and lessors
Hence the advice I have given :

if you so wish to DIY then by all means do so. At the end of the day it is you that is taking responsibility and no one else
Try to emphasize that fact that you are the person responsible. Had a conversation with a good friend and client today. He is a qualified plumber and does renovations. Specializes in water proofing / painting and then also does sub-contracting, hence being my client. He phoned to ask if he could plug his generator in through a wall socket as he heard this from one of his friends on a boating trip. He decided to phone me and ask for advise and what the implications will be in doing this. As a good little electrician I told him the ins and outs as per regulation requirement and also the reason for this requirements (as not everyone listens to rules...) he then decided as he has to little kids and a wife and a maid and a rental apartment attached to his property that it be better to do it right.

I will never force or convince a client to do anything. I will always just make sure they understand the implications of what they are about to do and let them make the choice as the responsible. I will also never do anything for a client that in accordance to my knowledge of the regulatory requirements will be seen as illegal and unsafe. That is maybe where I loose alot of work, but hey different folks different strokes.

I cannot see how it would be a problem
Personally and not according to regulatory requirements. And this saying if the regulations have been followed and the installation is safe, I am happy.

Just remove what you have done when selling the property or changing ownership so as to avoid paying alot to have everything certified
This is probably a more obvious point of view. I mean you really only have one of these to choices when having done the installation yourself if you aren't a registered person right?

Just make sure you have sufficient knowledge on how to DIY and what the requirements of the relevant regulations
Sufficient knowledge on how to do it yourself and what the requirements of the relevant regulations are can only be approved by the chief inspector. This is not something you can decide for yourself.
Therefor just make sure you have sufficient knowledge. Hence the reason one is required to complete the requirements as set out in the OHSA - Registration as registered (revised March 2014) person in order to be deemed a person of sufficient knowledge of relevant regulations

So please do excuse the sarcasm of my previous post