I see no good rationale to modify a cd/dvd player for better DAC. If you need a better DAC doesn't it make better sense to just add the DAC and use the player as a transport? Essentially that is what your then using the original player for. I just think depending on what mods you do to a piece of gear, it could loose all its value if you ever wish to sell it, as you'd have to find a buyer that not only wanted the original piece of gear, but who appreciated the mods too and was willing to pay a premium for both. Meanwhile just adding a DAC, you always have two stock pieces of gear, worth whatever their worth, with no 'story' to tell to sell them.
Also, having seperate gear you can always upgrade one without the other.
I dunno though, just my 2 cents worth.