No safety concerns between P2F and safety? Who said that?
Theoretically, it could be very safe. But that's because theoretically a person with a lot of natural ability could go down that route.
The reality, however, is different.
Because the CPL is a basic flying qualification and ATPL exams are easy, any person of average ability can gain the required licences to apply for a TR plus 500 hours course. All they need is money. So, yeah, I'd agree with Gilles that P2F is a safety concern because airline imposed recruitment standards are too low.
Yet, I'd venture to suggest that the likes of AirAsia and Lion would be having over-runs irrespective of the use of P2F cadets. The reality is that the environmental and cultural conditions in that part of the world are demanding and there are a lot of poor pilots flying for those operators for whom the use of P2F is merely a slice of an otherwise poisonous pie.
Thankfully, the likes of the European low-cost airlines are not in this category because they are able to sift through all the chaff in order to find the wheat. To back this up they generally have good initial and recurrent training regimes and robust SOPs. Their safety records speak for themselves.