is it possible? certainly. likely? probably not.
as i understand it, at the moment porteus has three core devs, covering five desktops, kernel drivers and documentation etc(and their day jobs).
the general trend is finding ways to do less, not more.
which is a good idea, no point in taking on more than you can handle.
so unless you or somebody wants to step in and build it......
that said, what is more likely, as dustbunnies aludes to, is (for someone) to make an addon module for lxde( or another desktop,depending on what apps you want) ..as a community project.
here
http://forum.porteus.org/viewtopic.php?f=75&t=2471 is one i made to utilise openbox and add conky tint2 spacefm etc..
and here
http://forum.porteus.org/viewtopic.php?f=39&t=2232 is a 'how to' for that.
unless, you want some specific apps you prefer, since fluxbox itself is just a wm and panel.
and thats the question, what sort of fluxbox do you want? which bells and whistles(filemanager etc)? or none at all ?
build it yourself and you can have exactly what want
neko's fvwm module is a good example.
i have made a fluxbox module, using usm, but all it is, is fluxbox with some configs atm.. built atop of lxde+openboxaddon.