I did some crude mock ups of what two popular, modern-retro style ballparks would look like if built on the SkyDome lands. I chose Camden Yards in Baltimore and PNC Park in Pittsburgh as both stadiums are smaller footprints that would best be suited to the limited land availability in Toronto. Both are also widely considered to be the gold standard of what an MLB ballpark should look like in terms of layout and design. Other newer parks take up too large an area with dimensions far larger than those listed below. As a disclaimer, I measured the entire lot lines of these stadiums, which includes sidewalks and other structures that surround the stadiums themselves. My estimate is that a new stadium on the existing Dome lands would be built south of Bremner and stretch north and east accordingly.
PNC Park dimensions:
Capacity: 38,747 (seated); 40,000+ (standing room)
Home plate (NW corner) to RF corner (end of Mazeroski Way meeting Three Rivers Trail): 207 m
Home plate (SW corner) to CF straightaway (Three Rivers Trail meets Roberto Clemente Bridge): 338 m
Home plate (SW corner) to LF corner (corner of Federal St and W General Robinson St): 277.55 m
Camden Yards dimensions:
Capacity: 45,971 (seated); 48,187+ (standing room)
Home plate (SW corner) to RF corner (B&O warehouse): 216 m
Home plate (SW corner) to CF straightaway (W Camden St): 348 m
Home plate (SW corner) to LF corner (Brooks Robinson statue): 280 m
SkyDome land dimensions (south of Bremner):
Home plate (SW corner) to RF corner (Pumping Station & Rees St): 218 m
Home plate (SW corner) to CF straightaway (northern steps at Robbie Rosenfield Park/CN Tower entrance): 322 m
Home plate (SW corner) to LF corner (corner of Blue Jays Way and Gate 14): 270 m
Here's what PNC Park looks like superimposed onto the SkyDome lands:
The dimensions of the structure certainly fit, especially on the southern portion of the lot.
Here's what Camden Yards looks like in the same area:
Similar to PNC, the dimensions certainly fit. It remains to be seen how any proposal would affect the pumping station at Lake Shore and Rees St. Would the station be moved underground or somewhere else entirely? Furthermore, Bremner Blvd in its current state would have to either be rerouted underground, which doesn't seem likely, north of the new stadium, which also doesn't seem likely, or disconnected in between the stadium. Perhaps Fort York Blvd gets extended east of Spadina and the new Bremner begins east of the new stadium. Additionally, any stadium proposals of this nature would likely include an extension of Blue Jays Way south, ending with a cul-de-sac at the SW corner of the stadium. Perhaps John St gets extended over the rail corridor and also ends in a cul-de-sac before the stadium's CF plaza begins.
Saying all that, any residential and commercial real estate developments are fairly limited in any such instances. PNC's dimensions leave about half the current stadium's footprint to build on. Camden's leaves you with barely a sliver. Any additional RE development would require utilizing the space overtop the railway. Whether Oxford's proposal moves forward remains to be seen but Brookfield's development of the Dome's lands would likely come right up to the property line with Oxford. Whatever new stadium Rogers and the Jays intend to build, it will also likely have to be more condensed than what PNC and Camden can offer.