My first thoughts we're.... well they have to at least say this and pretend they are doing it to get the FL to approve the ground share in the first place. The FL will only approve the ground share if they can demonstrate a plan to return to Coventry. This then allows them to continue with their current strategy.
If they are serious about it, then forget being back in the city in 3 years. Nice clever play with words that one, 'will be planned and delivered in 3 years', yep that's after the site has been found and purchased, appropriate financing is put in place, planning permission obtained and appeals heard if refused or objections put in. The FL would probably give them 5 years to get it done, but if they don't what really are they going to do, if it's progressed a certain way, they would plead against the various delays not being of their making and in all likelihood the FL would give an extension. All in all you could be away for some time, 7/8 years maybe, who knows?
In terms of location, immediate Coventry area can mean anything. The use of the words 'immediate area' is obviously meant to make you think in the city but in reality is often misused (sometimes deliberately) as a substitute for 'in the vicinity' which puts a whole different spin on it. I doubt very much if it would fall in the area where planning is controlled by CCC. They would obviously fight any planning rejection but if they are serious then why give yourself the problem, cost and delays in the first place.
My final thought was you may have the revenue streams from such a new stadium but forget any major investment for some time from this as it would most likely in the main go to paying back the investment in the new stadium at least in the short term. The worrying possibility would be to build it, then use it to leverage lending to pay back the investment immediately so they have their money back and so eliminate risk, then the revenue streams that are supposed to give you an advantage in the main just go on finance payments and the debt sits with the club. This could then extend into you just becoming an investment vehicle where the model is basically what is the minimum investment we need to put into the team in order to deliver the highest yield with that profit just going to the fund which holds a charge over the club for funding the stadium (cash cow). Ask any Saddlers supporter the question 'how is the only way you can make money out of a football club without them being in the top of the prem or having to gamble the millions needed to get them there?' and they will give you an example of this model.