The opportunity to speak during Statements by Members is allocated to private Members of all parties. In according Members the opportunity to participate in this period, the Chair is guided by lists provided by the Whips of the various parties and attempts to recognize those Members supporting the government and those Members in opposition on an equitable basis.
Nothing in Standing Order 31 establishes that the Speaker be so guided. And so the Speaker should simply abandon party lists and ask MPs to submit their names to his office, at which point MPs will be called on in the order that their submissions arrive (with the same allowance made for a balance each day between government and opposition statements).
This would also have the effect of making it a bit harder for parties to stack those 15 minutes each day with partisan harangues.