I can only presume the big clubs spurned the original RFP because of the crazy contingency fee floated (wasn't it $100K / squad?), plus all the other stipulations. It was WAY overdone, and way too administrative heavy.
What you describe can be accomplished over two seasons w/ way less barrier to entry, assuming you can move the season to summer after year 1.
Gotta remember, largely, what makes football in this province go around is volunteerism, not professionalism. The volunteers make it happen.
Try telling the better run clubs now (pick any), that in order to be involved they will need to potentially triple their workload? Oh, and in addition, we need to come up with crazy financial backing?
Who in their right mind would do that?
Maybe three or four, and those would be:
~TSS
~Highlanders.
~PFC
~WCFC
Now you only need 6-8 more clubs. That's either 6-8 start-ups, or 6-8 clubs willing to triple their work load, because presumably those clubs would want to hang onto their current Premier programs as it sits now. Why wouldn't they?
Come on.
The common denominator in all this is that typically guys will want to challenge themselves to play at the highest possible level they can...by and large. For (I'm guessing) 80%-90% of the players, this is their desire.
That is also the common goal of this league, because even if it has a development mandate, the best way to develop is by having the best players around the kids, and making kids earn it. A development league limited to kids under 23, as an example, won't develop the best young players. The competitive environment already established w/in the three leagues is exactly what this Tier III league needs. You want the kids to rise up to Soolsma's level, not be content being the best striker on a summer university circuit.
So, you start by removing all barriers. Throw the RFP stipulations out. Simplify. Call it Amateur. You should be able to ask for- at the least- all home parks to have adequate change rooms, and ideally, viewing stands. Most big clubs can come up with that as it currently sits now.
The one carrot the Tier III league has that would entice over the players- and encourage clubs to pull their Premier teams and enter into the new league- is the opportunity to compete for a Canadian Championship. Get it done. Fcuk the existing three leagues, frankly. Pull over the top 12-14 Premier League Teams / Clubs, and you will force these three leagues into a new reality, and likely collaboration. This can EASILY be done if clubs desire it. The clubs hold the power when it comes to getting fields, not the leagues. Presumably, for example, CCB would hold a tremendous amount of clout, as would Surrey United, Abby, the big Island Clubs, and CMF. Why? Because they have the registrations. Simple as that.
The three leagues have not been involved in this, and that's fine. Establish parallel league schedules to start (removes one big barrier of entry), and fly at it. The leagues would be forced into restructuring, and that's fine too.
Fcuk man, you can "invite in all the stakeholders", and "work towards a sustainable, successful model", and "add in more corporate speak here". Fcuking hell, sometimes you have to actually just go ahead and shoot first, ask questions later. Get 'er done. It's really so simple it's maddening.