It wouldn't be fun if you didn't re-invent your own wheel but this time did it with the features you want instead of the ones that are almost-identical-but-you-didn't-invent!
http://tutorials.jenkov.com/iap/ion-vs-other-formats.html
Not every innovation is from scratch, or 100% unique. MessagePack was designed as a binary encoding of JSON. CBOR too. ION was designed to be a binary general purpose data format able to mimic both JSON, XML, CSV and raw bytes (files), plus the most commonly used data types.
Of course there will be similarities when we try to tackle the same problems, but we also believe we had added something new and useful to the mix.