I think the whole intention was to get their Diamonds from doing GE1-4 here. No Plundering means all their Goods production is safe making it slightly easier to unlock all 4 levels every week.I don't think it's really abusing the system. You're limited to 1 win of diamonds in questlines once per age.
They'll sit in Iron Age without access to pvp and camp, and they can't be plundered. But they'll be in iron age with very small cities and without presumed access to chateau they won't be netting much in RQs. They won't earn much coin/supply to do the unbirthday, etc. Butchers are too big to do item quest efficiently. I could go on.
I don't think the impact is significant at all.
And as for doing RQs in IA it’s actually quite lucrative. LoA is small and can fit in easily, alongside Babel to lower the need for Cottages. Then getting SMB won’t be too terribly bad since there are players already in LMA (and well above now I presume), so finding prints/goods won’t be too difficult a task. SMB will allow their small pool of Cottages to greatly increase coin production, enough levels and it will out pace supplies easily, even with LoA boost to Butchers.
That makes doing UBQs actually pretty easy. And I understand that some players are sprinting to obtain Traz/Arc prints to be the first with both, which means Chat prints will also be available to anyone that wishes to get them. The goods might be slightly more difficult, but doable over time.
What one could now do is have a Goods production farm, with a very small number of Butchers, work on leveling up their Babel with daily fps. By the time they get to the point Chat prints/goods are available they will have several thousand IA goods, enough to trade up for SMB goods, and have prints ready to build LoA, SMB and Chat all in one go. Chat will level itself in the lower ages if you advertise it to friends and Hoodies in the lower ages since players will Be after those prints, and the better medal/fp pack rewards it gives. That leaves you to then focus on SMB/LoA primarily since Babel will more than likely already be Level 10.
SMB/LoA to 10 means you can focus solely on Chateau to higher and higher levels, so if you felt like spending the day doing UBQs you could and not worry about losing coins/supplies, while gaining the medals/goods/fp packs. Then if you so chose to you could Age up and immediately deploy a Shoemaker farm and skip building Goods Production Buildings altogether, since you would be able to continue doing all the UBQs you ever wanted to do, and get all your Goods straight from there making your goods still unplunderable. And you can continue doing so up through CA. IndA would be the phase where fighting becomes more of a requirement, unless your Chat is high enough at that point you are still gaining large amounts of goods/day strictly from RQs/UBQs.
Let’s also not forget having a level 10 Chat means diamond rewards from RQs will net 50/Quest, so an easy 500+ from all EMAA and up from the RQs from each age (assuming you will delete troops from GE rewards to do the 3 troop RQs as well). Followingnthat strategy your Chat could easily be getting into the 20-30 range in no time at all (another 10 Diamonds every 10 levels on Chat)
So actually not a bad strategy if you feel like never spending a dime on the game and can wait to obtain the diamonds through gameplay.