You definitely do not want to wait until after you are arraigned (i.e. enter a plea) before arguing lack of disclosure. You should review the Stinchcombe decision by the Supreme Court where the court expressly states that the defence should bring to the attention of the trial judge at the earliest opportunity the lack of disclosure so as to avoid a new trial. So, clearly, if you have not received any disclosure before your arraignment, you should be raising it before entering your plea.
Regardless, in order to obtain a Charter remedy, you must follow the proper procedure and filings. You can't simply raise such issues in court and expect to receive a remedy. After all, the Attorney Generals of Canada and/or the Province of Ontario may want to challenge your application and they have the right to not only be notified of your application, but to speak at your hearing. As such, the court loses its jurisdiction to proceed on such Charter application until such procedures are followed.
Furthermore, by entering a plea, you are actually indicating to the court that you are making an informed decision and are ready to proceed to trial. That is, all preliminary matters such as disclosure have been resolved. Therefore, some judges take the view that you lose your right to argue for any pre-trial entitlements after you have been arraigned. Generally though, the court will simply adjourn the trial and order the prosecution to give you disclosure. You definitely won't get a stay since you are now also to blame for having wasted the court's time (by proceeding to trial when you were not ready). Of course, you'd also not get the stay for lack of disclosure since you wouldn't have followed the procedure for applying for a Charter remedy (such as a stay) so its a double whammy against you. But, because you also entered a plea and are now within the trial stage, you seriously challenge your 11b rights. After all, you can't argue unreasonable delay since your trial is already going!
Therefore, you either have to decide whether you are going to formally request a section 7 stay for lack of disclosure (which I think at this stage is quite premature since the court will likely just adjourn the matter for the Crown to comply) or hope that by adjourning the upcoming trial to another day, an 11b remedy might arise due to the added delay; thereby putting you outside the reasonable delay range.
Right now, the probability of you winning on either is quite low. Your best bet is to formally request disclosure by registered mail, appear at your trial date, request an adjournment for either not having disclosure or not having had time to prepare and hope that an 11b will be triggered because of the time it takes to get to your 2nd trial date.