You could try the "Aircraft (reload) function by assigning a key or key-combo to that function
in the FSX Controls menu. Look down the list for the command...they are in alphabetical order...
and assign you key choice. You can then use that to reload the aircraft while still in freeflight, or
even in multiplayer.

This will reload the aircraft.cfg file and panel.cfg files. It may not do anything for scenery overload
issues, however.

I use Ctrl + ' as my key-combo for that function. (control and apostrophe)

EDIT: To reload the scenery, go to the drop-down menu (Hold down the ALT key until it appears) and
then got to the 'World','Scenery" menu and simply click 'OK' when you see the Scenery Library menu page.
This will rescan the scenery.cfg file and reload the current scenery.

  Paul