Only way to solve the problem is to add competition. Yes, that means more cars on the road...
Just look at what TNVs did to Taxis...
What the FX (now UV Express) once did for the long Jeep ride
We once had a fleet of Jeepeneys... An old dilapilated jeepney will earn as much as the newly assembled one! And they will almost share the same surplus parts.
Requiring Euro-4 engines will not work since they can always replace the injection+cylinder head to make it run manually... Engine block+papers will say Euro-4, but emissions testing will give you a different result.
Stricter emissions testing will also not work since you can make adjustments to the injection (less diesel more air) to pass the testing...
If LTFRB starts providing franchise to A/C Jeeps (mini buses), Electric Jeeps with cashless payment, competition will later eat up the market and operators will have no choice but to upgrade.