Shouldn't you better hope for a PS developer? Aww sorry, I forgot...no active devs left...
There is one very important file to configure text sizes of PS: "data/gui/styles.xml". There you can change almost all default font-sizes for every GUI element in PS.
For example changing
<!-- Font used for all standard (non-editable, non-clickable) text -->
<style name="Standard Font">
<font name="/planeshift/data/ttf/LiberationSans-Regular.ttf" r="121" g="147" b="42" size="9" shadow="no" />
</style>
to "size="20"" will give you this:
But as you can see it also causes some problems like in the Info-window. Almost every window in PS is coded with a fixed size and can't handle changes of the font size so you are bound to run into problem with text not fitting in a specific area.
Still, in most cases you should be able to find font-sizes there that at least allows you to play the game to some extend. You can change the size of the font for almost ever gui element there, including buttons, text input boxes and even the floating name and guild labels in game. You also can switch to another font there but keep in mind to use the PS notation for the filename...meaning you have to use "/" to separate directories and you can only access folders that are below the installation folder of PlaneShift.
Reminder: If you change styles.xml always make a backup of your changed files. The updater of PS will most likely overwrite your changes with the next update again. Oh..and depending where you installed Planeshift you might need administrator/root rights to edit that file.
Now for orientation in game...mhh...all textures used in PS are inside "art/materials.zip". So it should be possible to change some wall textures there to simpler versions with higher contrast. But it will be for sure some work...and this is part of the PS art so the ABC license forbids to publish modified versions, meaning you are all on your own with those changes (What reminds me...most likely anything I say here is seen as modifying the client what is forbidden. But I assume nobody will really enforce this policy in this case...heck even I was never banned for using a modified client and only for speaking out too loud). I can just assume that changing for example the skins textures of "characters" to some brighter color might make it easier to identify them against the background. In case you want to change some textures just unpack that zip file somewhere, edit the textures (but make sure to not change their filenames), save them as .dds (Direct Draw surface...I think most image editing tools support that format...gimp does for sure) again, then package everything in a materials.zip file again and replace the old one with it.
And last but not least...a compass or mini-map. Good luck with this one. Both are discussed for many, many years now. I have seen some pretty sophisticated suggestions for a compass system including the math needed for a polar coordinate compass system over the last years. But even in times when PS actually still had some active devs none of those suggestions ever made it in the game. So...I wouldn't count to see a compass or a mini-map within the next ten years.
Edit: Typos