Always stick to the OEM size rims regardless of the case.
The disadvantages in increasing the size of the rims in my opinion are as follows:
The suspension of the car will be badly affected in the long run even if the current condition of the car's suspension is good.
The fuel economy of the car will be badly affected overall.
The speed-o-meter reading will also get affected as it will not give you the correct speed of the car, for example, if your car is running at 60 km/h, it will show you around 80 km/h or 40 km/h.
The overall comfort of the car will also get affected in a way that you'll experience a bumpy ride.
These are some of the main disadvantages among others in my opinion. So, I suggest you stick to the OEM size rims and it will be beneficial for you in the long run.