That's a shame. In that case, it's probably best to stop using the term 'line-out' from this point on since there won't be one. Just too confusing.
This is a bit of hopeful thinking. You can mitigate the affects of a pot (such as miller capacitance, etc.) by reducing attenuation but it never disappears. The best way to test this is to run a DACPort LX versus a DACPort into a transparent amp w/ a solid transducer. Now adjust the DACPort pot how ever you like to replicate the transparency of the LX. It can't be done. I've read that HPA even likes his DACPort more than the LX for his tastes but that confirms that they do not sound the same no matter what you do with the pot. The non LX will sound more colored. Whether you prefer that or not is another question entirely. Those that care about a line-out, care about a line-out, not something trying to behave similar to a line-out. Just sayin'.
Anyway, I'm in even if it's not 100% what I'd like but what is in life? Besides, if it doesn't work out for me, there's always options.