I doubt it is possible to convert any brand of writer to another regardless of using same components etc.
It's the firmware that makes everything work and firmwares cannot be migrated to other brands e.g a pioneer firmware into a nec etc.
Bottom line is many people bought 8x writers as soon as they were released which always a mistake.
It's better to allow all the top manufacturers to release their drives then read reviews about the drive to make an intelligent decision.
With a pioneer you always have the added bonus of a patched being released fast which turns it into a cracking drive afterall with the patches pioneers would be crap as the firmware restrictions cripple the drive whereas other brands will allow a certain amount of overclocking of media as standard.
This overclocking means media prices have to fall afterall if you can a decent burn with certain 4x media at 8x why buy 8x,sure it will be rated but thats the only difference and when 12x comes you can bet 8x media will burn a treat.
When 4x media first arrived it was very costly i doubt 8x will be much more expensive than 4x is now simply because so many people will be using overclocked 4x media that too big a price difference will mean very slow sales.