I don't think this or the money will make any difference.
I think a browser is too big to develop for one team and I think the Firefox browser is too alien for one team to hope to port to Amiga-like OSs.
I think it would be better to have a series of AROS bounties aimed at making the underlying technologies available through an API;
Eg: HTML and rendering
CSS
Javascript
Java
HTTPS
etc etc
This way each implementation would make it trivial to develop a browser with that functionality.
With this API we could finally, as a community, stick a finger up to all the buffoons and racketeers who revel in embarrassing us on a monthly basis on OSNews etc. :-D