1. Do you think attacking clans should have a minimum number of active players to be able to issue an attack and, if yes, how many? If “yes”, then should trial members be included in the numbers?
Yes you should certainly have a minimum number of attacking players and you should not allow Trial accounts to make up those numbers, if you do allow Trail accounts you will only enable a means to circumvent the system you are trying to implement. The number of active player you need, is for me a finger in the air job, you could have a minimum requirement for each size of siege stone, small = 10, medium = 20 and Large = 30+ active players.
2. In the case of several attackers: What do you think the defenders should have to accomplish in order to win the challenge? Destroy the attacker clan stones (or siege stones), or to simply destroy siege stones placed?
The defender should never have to make any attacking moves at all, I know this is not true to real life, but as a defender you one and only goal is should be to prevent the attacker from destroying the City clan stone. The attacking Siege stones should provide bonus attribute to the attackers which can be destroyed by the defenders but if all attacking siege stones are destroyed this should not be the end of the Siege, this should continue until the City Clan stone is defended (certain defined time, increased by the attacking players Siege stone size (small 1h, Med 2h, Large 3hrs)
3. How do you feel about the timer running out without any of the sides having accomplished their goals? Should the defenders get the chance to both keep their city AND win the wagers for a successful defence?
The defending clan and their respective City will not have spent any capital costs by defending and as such the defenders should only retain their City holding and the wager should not be won, the attackers on the other hand, should lose everything.4. What do you think of an attacker’s city not going vulnerable automatically but the need of having to issue an actual attack on that city? (with the option for the defenders getting a free attack option without having to pay a fee).
The attackers city should not become vulnerable, unless Sieged. Period full stop. Then siege rules will apply, preventing any way to circumvent the siege system