Hi! I am new to Achaea and am finding it great! I can really see how much potential there is for adventure and genuinely interacting with other people in a roleplay setting (I wish I had known about this earlier)
Taking a look at different ways to access Achaea I had a try at using nexus in mobile.
I can see a way that nexus could easily be adapted (conceptually) to show the full UI that is available to players on Nexus. - Simply stack the windows available in the browser based nexus, on top of one another. Doing this there should be no real reason why you couldn't have the full experience on mobile.
I made a little image to help explain how this could work.
Obviously a more native app would do a better job. but I think just positioning the windows in a stacked fashion might work fine on a webpage without needing to add too many additional features to support mobile.