This isn't intended to be an argument against anyone else's opinion but is just my opinion.
There are several factors that affect the cost of a stadium; some will significantly impact the enjoyment of an event and others will result in a big cost with little return.
There are a couple of stadiums that I think should be considered as a models for Halifax but with some changes. Akron's InfoCision Stadium has a great layout and several VIP suites. It also includes a large classroom building, which isn't required in Halifax but inflated the cost. The other stadium is Stanford Stadium, however, only 24,000 sideline seats are required (not 50,000, including corner and endzone seats). Both of these stadiums are relatively low cost (in the vicinity of $2,000 per seat total cost when built - but this doesn't included parking and land cost).
I think that Halifax should build a basic two tier stadium with all folding seats. Folding seats aren't just for comfort but more importantly provide easy access to seats in a packed stadium. Economical folding seats (not plastic bucket seats) would add about $100 per seat over bench or plastic bucket seats. So for a 24,000 seat stadium that is about $2,400,000 dollars. This will greatly increase the spectator experience a relatively low cost (however, the stadium must be built to accommodate such seating).
I also think that an abundance of washrooms will greatly add to the enjoyment of a basic stadium and will allow for temporary expansion for larger events. (or in other words, portable toilets shouldn't be considered even for temporary expansion)
Only a limited number of permanent concessions should be built. BMO Filed has a high number of temporary concessions and give a fun atmosphere to the stadium. Cutting down on the permanent concessions makes sense in a stadium that will likely only see 10 - 15 large events a year.
A partial roof would be nice but isn't a necessity.
The scoreboard can be kept modest in the beginning until a better one can be afforded.
In-stadium restaurants won't make much sense in a stadium at Shannon Park where few people will go on non-event days.
Forget about all enclosed concourses such as in a hockey arena. This isn't enjoyable on most pleasant days and will cause the stadium to skyrocket in cost. This isn't because it costs more for material to enclose a stadium but because of fire safety requirements when thousands of people are in an enclosed area.
Minimize the complexity of the stadium but not the number of seats. Forget about an iconic stadium and focus on a functional stadium. In other words, don't use the new Winnipeg Stadium, Regina proposals, BC Place, Rogers Centre, etc as the stadium model. Consider half of the new Stanford Stadium as a model -
http://en.wikipedia.org/wiki/Stanford_Stadium
The thing to remember is that a large 24,000 seat stadium will likely only be used for 10 - 15 large events a year, even with a CFL team. Can Halifax residents accept the idea of building such a large structure for so little use? If the answer is yes then build it at a sensible price.