I agree. I would do the xc's/time building in the cheapest plane available, then do 10 hours complex/comm. maneuvers for the checkride, since he needs the complex time anyways.
I said I didn't think it would be enough for them to transition, some can, others just get lost in the pattern when moving to a complex aircraft. Basically I don't think 10 will be enough for every student, but in 10 hours you can do 1 cross country and the rest maneuvers in a complex. Remember though many complex aircraft have a large speed difference over the cheap aircraft so it isn't as large a gap as it seems.
My thinking is for cross countries using the cheapest high performance aircraft on the line over the cheapest regular aircraft on the line is beneficial and the cost difference is minimal. From there if the student wants to invest more and see more complicated systems they can.
152 = $90/hr | cruise @ 5k abt 105
PA-28 = $114/hr | cruise @ 5k abt 140 | DME
PA-28 (2) = $129/hr | cruise @ 5k abt 140 | 2xGarmin 430/GPS
172RG = $139/hr | cruise @ 5k abt 140 | Garmin 155 IFR/GPS
172RG = $149/hr | cruise @ 5k abt 140 | 2xGarmin 430 GPS/SANDEL
Now lets say a 250 NM cross country for the commercial.
152 = 2.4 hrs cruise + 1 hr = 3.4 * 90 = $306
PA28 = 1.8 hrs cruise + 1 hr = 2.8 * 114 = $319
PA-28 (2) = 1.8 cruise + 1hr = 2.8 * 129 = $361
172RG = 1.8 cruise + 1hr = 2.8 * 139 = $389
172RG (2) = 1.8 cruise + 1hr = 2.8 * 149 = $417
My point is for 13 dollars more your student can fly this flight in a PA28 not to mention in less time which for most people, time is money. The one hour alloted is for time to depature/climb/descend/approach and land.
I just push my students that are at the commercial level, they are going to be working as charters/sightseeing flights or possibly flight instruction so I personally try to prepare them for that. Having your student get in the aircraft take you to another airport to "pretend pick up a 2x pax + you and the cfi" and then taking them out for a photo ride to a near bye location maybe 20 or 30 NM away can be a good real world commercial mission.
He will have to have a weight and balance and find a spot on the map using whatever equipped aircraft he was in. This is a flight I have had working for a local FBO, granted it was 3 pax not 2 w/a cfi simulating, but you get the point. It would help prepare them better in my experience and thats what I want from people that are on my certificate.