What I can more or less guarantee for the not too distant future is a conversations view that shows all tweets from the current one up to the root one - if the displayed one is a reply. If the displayed one is a "root" tweet and you want to see all replies to it, it will be a little bit complicated as there is no API for that. I'll need to implement a workaround that will most certainly only work if the displayed tweet is not older than 7 days. And even then, the view won't include all results as the search API only operates on a partial set of the tweets from the last week...
Selection bar at the top: In theory you could make this configurable, but there is so much to implement concerning other features that I don't see this happen anytime soon