I came here just to say what others have - a web version would be killer. I'd even pay extra for it.
An extremely important feature, probably the most important one, along with mobile apps. As someone who works mainly with a Chromebook, an online version is a must.
The WebApp version would allow me to access my cloud documents from anywhere. Specially on those moments I wasn't expecting to do it. It would also grant mobile devices the capability too.
I think that even a readonly alpha version would be an amazing start point. Carring a pendrive is not the solution, I'm carring my mobile device everywhere.
The present/future is cross-platform software or cloud software. Have in mind that I could access Write! from my smart TV.
You can have the soft as a portable app on a USB key. That's what I do. The best could be to have a 100% offline version without having to log in.
An online version is, from my point of view, the worst thing that could exist: The company disapear then the app disappear with it.
Chuck Dee commented
This is what makes me continue to go back to dabble (https://www.dabblewriter.com).
This app so needs an online version. What if I am traveling through Tibet and finally get to a computer and MUST download the app. No, I say have an online version, where the website becomes the writing suite.