Keep the Downtown Terminal as a Bus Terminal
While I support the construction of the new hub at Allandale, which is sorely needed, I don't think that we should convert the Downtown Terminal into a market.
Terminals usually require density around them to support traffic. The distance between the two termimals is also only a 5-10 minute bus ride on Bradford Street.
Keep Downtown as a stand-alone bus terminal. If you want a market, expand the old Burger King and extend the floor space further and you can have a market in it separate from the bus station, perhaps with a separate entrance.
A more ideal place for a market would be to take one of the parking lots next to the Spirit Catcher and convert that into the market. You'd have floor space, parking for customers and delivery trucks, and a space where shoppers browsing for food rather slowly won't conflict with the bus passenger who's in a rush to make a transfer.
Logistically, having two central stations also makes sense, as you can spread out some of the load of buses between the two. A few cross town routes can serve both terminals, such as Route 8, Route 1 and Route 4, while other routes that primarily serve the north end or south end and serve residential streets (like Route 6 or the 2013-14 5A-5B) could terminate at the terminal on their side of the lake. This means that the load of buses we have currently causing traffic jams on Maple during rush hour as well as the long waits at Allandale at rush hour will be spread out, which is more efficient for passengers, motorists, transit staff, and the public at large.
In terms of Intercity buses, we can keep GO Route 68 and some all-stops Ontario Northland trips running out of Downtown, while the rest of the services would be moved to Allandale. At the same time, we could work with the County to extend their two routes to Midland and Orillia from their current termini in the East End (RVH/College) direct to Downtown, with two or three of the platforms being a dedicated LINX platform, which would offer timely connections for LINX passengers connecting to Route 2 to Wasaga Beach and Collingwood, through a simple quick bus transfer up Bradford Street between either one by a frequent Barrie Transit bus.
Another important point in favour of Downtown is the density factor. Downtown already has the most density in Barrie, it already exists and more is going to be built in the future. People who want to take the bus can wait in a safe, warm, comfortable terminal, have helpful staff answer any questions they need answered, and board a bus safe and warm when it shows up.
Another important pro-Downtown argument is that whenever there's an event Downtown, for example Remembrance Day, the Santa Claus Parade, or Canada Day or Winterfest, and especially New Year's Eve, the terminal has more than adequate levels of capacity for patrons of these events to wait for their buses, in safe, controlled areas, rather than on a crowded sidewalk outside the terminal like is planned.
Most European cities of our size have more than one central station. We can have both stations and meet the needs of the population, and not have to re-invent the wheel.
Keep the full amenities at both terminals, keep Downtown as a complete terminal, and yes, build the Allandale terminal. Both terminals have rock-solid cases to be kept as bus terminals/built as new ones.