Diplomatic change is not sagnificant change. It's difference is less adding more UU. It should not go instead of serious features.
And yes, DW is not FFH, and FFH's fail, imo, that they went way of neglecting MP. There are alot of players who wont play FFH, and still play civ b/c there is more challenge and balance.
That poll means nothing, and it show good percent of votes for mp .
While refining bonuses will not throw SP gamers, some stuff will throw MP gamers out. There are 1000 ways to add flavour, and insisting on adding more and more such bonuses - insisting on denying quite big populace playing mod.
Another stuff :
i think New culture system is too powerfull. With BG i can do amazing things, pop endless culture borders and take cities at will just by culture. Seems it is bit over-done. Need to tone it abit down.
Also i think 1st KH is too powerfull. It come so early and 25% to all stack - thats alot. Still, BG is easy civ to play now. I know it i compare it.
Perhaps 15% for 1st one will suffice
Small observation - they are like Tleilaxu but MUCH more powerfull
Lets compare

Religions - BTl cant convert BG Can, it have monopoly on Shai Hulud at current setting. I found SH on Immortal without any problem.
Plague of BTl? Well it is rivailed just by 1st Kwizatz - quite early, before wars even start...
What later? Later BG just grow more and more powerfull. For BTl, which is already powerfull compared to some other civs it will be too strong rival.
I think that KH line come too early and perhaps 1st KH is too strong.
I know that balancing should be done mostly through adding, rather than nerfing - but i think its a case where it need some tune down for sure.