I read the list of things you hope to implement by version 1. I have two suggestions but I am not a programmer so I have no idea how easy or difficult they would be to implement.
1) it would be awesome if your planned rss reader is able to import an opml file. Right now I'm using liferea to follow 100+ news feeds. Having to add them one by one by one in FF or Thunderbird is why I don't use those programs for newsfeeds.
2) please have a look at wire.com. It is a 100% open source voice and video messaging app. You may be able to integrate it's functionality in Otter.
Thank you creating Otter. Building a web browser must be a monumental task and I'm really glad that someone is willing to do it.
1) And OPML export. Data liberty. ;)