I have been told a couple of times, to come back with proper visa.
They always let me in.
The last time (a few weeks ago), they leaned on me, that I should get the proper visa.. This time they seem kinda serious. In the past year or so there are a lot of new and different visa options... I am sure you can find something that will work for your situation.
You can always do what you want. but if the deny you entry at the airport, where you go from there may not be your choice. They could deport you to your home country or they could simply allow you to fly to another country of your choosing.
It used to be less of an issue. I have "abused" the system with reckless abandon, but the last time I came in the immigration officer pulled me aside and read me the riot-act. He made a point that in the past they were more flexible but they now have more visa options so there is no reason to 'work the system'