I seriously can't see REX being a serious alternative for business travellers with an OTP statistic that will make Tiger look good.
If REX primarily do what is true to their name and look to serve regional passengers then their schedule could be quite doable with 10. Any capital city traffic they pick up would be a bonus.
The other thing Im interested to understand is if they might expand regional routes to make bigger banks into the city. Eg perhaps a Bendigo-Sydney or Mildura-Sydney flight on Rex (QF already has one) which might connect to the same SYD-BNE flight that arrivals from ABX, GFF, NRA, WGA, OAG, PKE, DBO might also be using? Perhaps a Moree flight can be added to existing Armidale, Grafton, Lismore and Ballina/Byron flights. Though in some ways they probably would have already had these in place if they made sense to do so - own metal on carry service to the other capital wouldnt have been a big factor in profitablility of these flights.
Regional on-traffic just doesn't appear enough. Let's assume that 50% of pax are transitting onto mainline services elsewhere in Australia( seems a little high anyway); that means about 17 pax from each arriving plane will be going onto a jet service. From there, these people need to be heading to one of the other 2 REX jet destinations (ie an arrival into SYD is heading to MEL or BNE) so the 17 may already be down to 12 or so and splitting between the two destinations that is only 6 pax on an arriving service into SYD that will be transitting onto MEL. From there, there will be natural deductions, someone flying into SYD from WGA won't be connecting to MEL because they can already do that with a direct service, same for ABX.
In reality, REX just doesn't seem to have enough regional services to support an albeit limited mainline jet operation flying 180 seat 737s and will have to rely on point-to-point travelers. As has been pointed out, most corporates aren't going to be too interested because frequency is poor compared with QF and VA. This means they are trying to attract discount pax who would otherwise fly JQ or use restricted but very cheap QF/VA tickets. I guess they could try to attract some leisure travellers but the 3 cities they are targetting are business focussed with limited leisure.
I'm not saying they definitely don't have a market to target but I'm struggling to see how the numbers come together. Their cost base isn't going to be particularly low, certainly no lower than JQ and probably no lower than VA2, their route structure is small and they don't seem to possess a unique selling proposition. Absent a VA2 and they were the obvious candidates to steal the market just as DJ did when AN folded but it appears very likely that VA2 will be a thing so that opportunity probably doesn't exist.
717, 721/2, 732/3/4/5/7/8/9, 742/3/4, 752/3, 762/3, 772/E/W, 788/9, 300,310, 319,320/1, 332/3, 359, 388, DC9, DC10, F28, F100, 142,143, E75/90, CR2, D82/3/4, SF3, ATR