You don't have to do anything so convoluted. Namecoin allows arbitrary strings to be included in its blockchain, retrievable by methods currently available in the client and through blockchain explorer tools on the web.

I could register a name ip/dc-invents-fire, and give the name the JSON:
 {"ipdocument-hash":"f196673ab59624b00c77c7f8e1764aa77665de6d44686d07d46650c9a61b4d1c"}

Elsewhere I could state that my message is "I discovered fire", and the SHA256 of that message is in block 123456 of Namecoin, proving that I invented on or before that block (which is timestamped +/- 2 hrs of actual time, outside of my control).

About the only thing quirky with Namecoin is that you have to pre-order your name 12 blocks ahead of actually registering the name with data. This little delay makes for some quirks:
- If you have an IP idea now, you can't publish your proof until after ~2 hrs (unless you planned ahead).
- Only the final registration can be considered the time proof, as someone could pre-order and have the pre-order waiting for the later "invention" or "discovery".

Name registration procedures, if you need a refresher:
https://wiki.namecoin.info/index.php?title=Register_and_Configure_.bit_Domains#2._Pre-order_a_domain_name

Looking up an example name with a block explorer website:
https://dotbit.me/block_explorer/name/id/deepceleron