Before you start spending hundreds or $ getting a bylaw professionally written get a copy of your current bylaws and see how many Special Bylaws are already registered, compared to how many alteration you can see or know about (I would guess their will be very few) within your complex.
The bylaw for these sort of small renovations just need to specify that you accept responsibility for the repair and maintenance of the renovation, simple as that.
In fact why not add a bylaw that states that you will accept responsibility for the repair and maintenance of all renovations and alterations you make to your lot. That way one bylaw covers you for future changes (subject to EC approval) as well.
Also when you register bylaws the cost is the same for registering 1 bylaw as it is for 10, so wait until others have a bylaw to register and do them all in one go and only pay 1 fee.