Guys, I've seen several concepts for overwriting\deleting 'old' or 'unnecessary' files. But it breaks the whole concept of Datacoin. Look: someone uploaded some kind of Wikileaks archive to Datacoin, then hackers who work for government accessed his computer got his keys and deleted this info. It will be practically the same as Dropbox\GDrive storage: if someone gets your credentials, he can delete any info he wants, it breaks the whole concept.
And I've talked many times about 'proof-of-storage', just now there are no ways to avoid cheating like creating bunch of VPS that are linked to one blockchain - 'I have 1000 machines with Datacoin', and actually it will be 1 copy of blockchain and many virtual machines linked to it.

Talking about colored chain - will it be secure and reliable?

I'm not arguing with you, it is just my point of view. I'm not head developer, maybe he will read our threads and see some features to implement. But just now I have opinion as described above.