Reinforcing unaligned players

As for Dunoobs comment, I am speaking of players not in any alliance who do not wish to or cannot join one. 

1) It's conceivable an unallied player might not *want* someone else's troops reinforcing. Perhaps a "wait at the gate" system could be implemented, whereby the receiving player has to officially "open the door" before the reinforcing troops are allowed to come in. Until then, perhaps they set up camp outside the walls. (which might have its own implications)

2) Re: Rill's point about one player thwarting their own alliance's forces. I believe you're saying that by installing some units in an unalligned player's towns, you'd "change the diplomatic nature" of that town and by doing so cause your alliance's attacks to bounce. That brings up interesting game dynamics, and there might not be an all-or-nothing answer. The two extremes are what you suggest (attacking troops bounce) OR that the troops within the walls are now under a different diplomatic banner and thus subject to the same attack. The simplest solution is that the attack wouldn't bounce, and neither would the *allied* (reinforcing) troops suffer the attack. Something like *they sit on the sidelines, watching the two forces fight it out, unable to choose a side. There's probably a fine balance between all three points and I'm sure aspects I'm not picking up on yet.

3) What happens when troops from two different alliances --non-allied with each other-- reinforce the same unaligned town? For that matter, what happens currently when two non-allied alliances reinforce the same town -- which *is* allied with both of them, even though they not with each other... 

Maybe if this "ability" were limited to the first 30 days of an account on the server or something?  Would have to have a mark like a rainbow to indicate whether the option was active for a particular player.

This problem could also be resolved by establishing a ghost alliance with an alt to which a couple of people have sitting privileges, allowing them to extend invitations.  Would be sort of a waste of an alt, though.

I think it would require a lot of thought.