Such savegames have been posted already. One thread I remember is
Just need a saved game, not a speech. (for obvious reasons
).
However, now we can look inside savegames and change them. So the question is: what should a 'free play' savegame look like? We can have free play in a fashion already via FLServer but SP mode is more flexible savegame-wise.
Ship == Starflier and $2000 starting cash can be arranged easily but the level question is a bit tougher. I am not sure we can make it so that you start with level 0 or 1 and still be exempt from story mission duty, so it could be that you have to start at level 18 and just earn a huge wad of cash to reach level 19. After that the leveling-up will be normal.
What about the visit flags? Should the savegame have 'visited' all systems, or just the mandatory story bases? It also makes a certain amount of sense for such a savegame to have 'visited' only Manhattan.
OTOH it is a royal pain in the neck if you load a post-campaign savegame to try something different and you have to discover all the systems/bases/wrecks/jumps/prices all over again ... But that is a different battlefield. I think we could make a utility that marks all things as 'visited' that you have visited in some savegame of your singleplayer directory - the sum total of your knowledge, so to speak.