Re: aikido vs jiu-jitsu
In my experiences, "aiki-friendly" might depend on who you study with. All the 6th Degrees in BJJ that I have studied with tend to be very aiki-friendly.
It's the white belts that typcially are not "aiki-friendly"...and that is also the case with white belts in Aikido...they are just learning.
Also, there can be a big difference in MMA and BJJ. Most MMA guys are not so worried about perfecting jiu-jitsu, but about learning how to deal with it...so of course YMMV. Is this what you mean?