After Kaiser, we can consider advancing against suboptimal. There's a reason he forward settled that city, while he has a lot of good spots closer to his Capital. The reason, if I'm seeing correctly, is that he has no other iron source. So, if we capture that city from him (and he has to keep a sizeable garrison near Rowain), we can deny him Mamluks.
The 2 horses sources are a big boon for us, since we can skip Encampments and still get horsemen. 75% production bonus is also no joke. I think we need to really use our military advantage while we have it, diplomacy be damned. This is likely a matter for 10 turns into the future, but suboptimal needs an Encampment before he can build anything more powerful than warrior/archers, so he's also a bit far from developing his military situation. If we have horsemen while he's still using clubs, we need to take the chance. That city won't grow past size 1 if we capture it, but denying Mamluks is a very big deal.
The 2 horses sources are a big boon for us, since we can skip Encampments and still get horsemen. 75% production bonus is also no joke. I think we need to really use our military advantage while we have it, diplomacy be damned. This is likely a matter for 10 turns into the future, but suboptimal needs an Encampment before he can build anything more powerful than warrior/archers, so he's also a bit far from developing his military situation. If we have horsemen while he's still using clubs, we need to take the chance. That city won't grow past size 1 if we capture it, but denying Mamluks is a very big deal.