The 757 can make it direct to Orlando (and has done so in the past, Air Scandic/Air Finland, for example), but it's right on the top end of the aircraft's range capability. Realistically if a 757 service operated to Orlando, who would operate it? Monarch's 757s are gone, and the Thomas Cook and Thomson fleets are slowly reducing their 757 fleet, and replacing with 737s, A321s etc. None of the US carriers are likely to do this, as we would otherwise see them offering Orlando to other European cities.
As mentioned above, once a week would suffice for Orlando, and more suitably on a 767 or A330. Daily flights would be overkill, as would Toronto on a daily widebody.