Do you have much experience of Asia? In particular, have you driven there? There any many challenges from the obvious one of simply managing to move without crashing to dealing with the police, breakdowns, accidents, parking, theft, etc. I drive in the Philippines frequently but I only do simple, familiar trips alone. For more adventurous trips, I would always have local friends and family with me.
Public transport is very good so it is quite feasible. By good, I mean it is easily available and reasonably priced. It scores less well on luxury and punctuality. Taxis are readily available and reasonably priced, use them to fill any gaps in public transport. In remote areas, the taxi may be a motorcycle with sidecar. I like public transport for solo travel, you get to interact more. Apart from my concerns above, I would not drive alone for this reason.
If you want the convenience of a personal car look for a car with a driver. It might be a similar price, it might even be cheaper and it will be a lot simpler.
This is based primarily on personal experience but I have spent a lot of time in the Philippines and I hold a local driving licence. This local licence helps: it reduces the "fines" if you are stopped and, in the worst case, if a cop confiscates it then you have not lost your home licence. This is only available for residents unless you have a very good fixer.
