So, given that I said we should junk and rebuild the Defensive Pact system I suppose I should offer an alternative, here's what I have.
Firstly - we get rid of the formal persistent pacts completely, that mechanic doesn't work for its intended purpose, it's biggest disincentive to further expansion is that it breaks your immersion ro have to face Christians defending against Muslims.
Here's what we have instead:
- Threat remain, it works more or less as it does now with one importance difference, realms start off with a "Base Threat" rating based on size. This new Base Threat will be something every realm will have, ranging between say 0-20%, and a realm will not be able to reduce Threat below that level unless it becomes weaker, either by losing land or suffering a major defeat that wipes out its levies.
- Threat will increase with conquest and expansion.
- Threat will decrease over time or as the realm shrinks.
- The rate at which threat increases or decreases will vary depending on how rapidly you expand or how long you are at peace. If you help your allies expand threat will reduce more slowly (but you won't acrue threat) and you'll be able to accelerate threat decay by helping defend allies.
So, that's how threat will work, but what will it be used for? Well - my thought it that threat will be a tangible measure of how threatening other realms find you. Instead of triggering Defensive Pacts your Threat Level will instead change how other realms react to your conquests.
If a realm has a high Threat level then when it initiates a new Conquest against another
smaller realm nearby rulers will get an alert and will have an option to join the defender in the war
regardless of culture and religion. Whether an individual ruler decides to offer support to the defender will depend on how they feel about the belligerents on both sides. If they like the attacker and dislike the defender, and are of the same religion as the attacker then they almost certainly won't join the Defender unless the attacker actually has 100% Threat. On the other hand, if they like the Defender and hate the attacker, but are of a different religion to the defender, they may decide to join.
If the Defender is joined by another realm in the defence which they are
not already Allied to they will have the option to propose Alliance and the other realm will be more inclined to accept than normally. If multiple realms join the Defence then the primary Defender will get an Intrigue option to propose a "Mutual Alliance" which will place all defenders into Alliance with each other. This could be a normal Alliance or it might be a special "Co-Alliance" which other realms can apply to join after it is founded. When a ruler dies his heir would get the normal "renegotiate NAP" option with other Alliance members.
A final note - following on logically from this I think it should be possible to propose an Alliance to someone you have previously fought alongside in war due to a mutual Alliance to a third party. The idea being that even without the Dynastic connection you have formed a bond through working together in the current war.