Bear in mind that although li-po and li-on batteries are both lithium chemistry they are not the same and have different charging requirements. We generally charge li-po batteries at a 1C rate unless they are labeled to allow a higher charge rate but a li-on’s ideal charge rate in under 1C. 0.7C or so is the rate commonly referenced.
Li-on batteries generally have a charge limiting circuit built into them that will allow a higher charge rate for a portion of the charge period but the circuit reduces the charge rate after the cells reach a certain temperature and capacity level. To prevent the battery from being damaged by a high charge rate the circuit will terminate the charge cycle when using high charge rates before full capacity is achieved. The faster a battery is charged the faster cells heat up due to resistance and the charge circuit reacts to resistance and limits the charge cycle. A fast charged li-on battery will indicate being 100% charged but not have reached full capacity when the cycle terminates due to sensed resistance. A li-on charged at a lower, recommended rate will last longer that a fast, high rate charged battery because the lower charge rate allowed the battery to reach full capacity, and balance when multiple cells are employed, by not having the charge cycle interrupted by the protection circuit.
Short version; you can only charge a li-on battery as fast as it will let you and the faster you try to charge it the less use time you will obtain from it. Those that have long flying days that are inhibited by ST-16 charge times might consider obtaining a second or third ST-16 battery and change them out as needed during a flying day rather that trying to charge the battery faster.
After market chargers with lo-on capability are faster that the factory charger, and cell phone/tablet chargers are also faster than the stock charger but both are still limited by the battery’s internal charge circuit. We should accept that li-on’s will charge slower than li-po’s no matter what we do to speed up the process.