Why not tailor the AOW to meet his needs and let him sign up now?
You could run PPB as an adventure dive. Run it as the first dive, then build on that progress in each subsequent dive (5 dives of practice on AOW, rather than 2 on PBB).
My AOW courses are cumulative. By that, I mean that as each component is added it is then applied on every subsequent dive. They are not 'stand-alone' modules, as once introduced, the student is expected to continue applying and refining the skills they have learnt - as extra skills are added.
The key factor is that the student progressively takes more responsibility for the diving with each subsequent dive, adding further demands and tools on each dive. Once taught, the skills, protocols and procedures are used on all dives thereafter. It can made be as intensive or gentle as the student can tolerate- thus is beneficial for a wider range of divers.
There's a lot of supplementation in each module. The adventure dive is merely a 'vehicle' for introducing the actual learning that is needed. EANx and Deep are especially important in that respect; as these really can cover gas management and dive planning to a refined level.
An example of cumulative AOW:
Dive #1 - PPB - Student is then to apply buoyancy and trim
Dive #2 - Nav - Student is then to navigates the dives
Dive #3 - EANx - Student learns gas management
Dive #4 - Deep - Student is then to 'more advanced dive planning and proper ascents
Dive #5 - Wreck - Application of all skills on a self-planned and managed dive, in which the student is the 'dive leader'. A real 'check-out' dive, done on a deeper wreck with proper planning, gas management, navigation and refined procedures...all the while demonstrating proper buoyancy and trim.
Normally, I'd suggest an extra PPB dive. That'd mean the first day was ALL about buoyancy and trim... core stuff. They'd have the option to get the PPB specialty card if they desired it... I can do a 2nd dive, or repeat the 1st adventure dive, for PPB as I "might interpret" that the student hasn't met the performance standards to a level of "mastery".
How I'd schedule it:
Day #1
AM - PPB - shallow water skills (60-90 min depending on student SAC)
PM - PPB extra - shallow water skills (60-90 min depending on student SAC)
Day #2
AM - Nav - shallow water skills (60-90 min depending on student SAC)
PM - EANx - 18m dive, planned for student SAC, using EANx32
Day #3
AM - Deep - 30m dive, planned for student SAC, using EANx32 + Pony
PM - Wreck - 30m dive, planned for student SAC, using EANx32 + Pony