it's not a "some of this, some of that" issue, as you put it. It's a standup / ground issue. If we were saying "train tkd for foot speed, thai boxing for power, boxing for strikes, karate for power and wing chun for trapping" then I would agree with you, because they are all standup styles that all have different principles.
however, we are talking about standup work and ground work. bjj mechanics will not confuse your mantis ones - you are in two completely different elements.
being realistic, mantis ground grappling may not be completely worthless, but bjj, catch, etc. is much better. Why? because it's what they do. you are trying to use your principles to figure out how to do what they have been doing for eons.
some grappling schools will teach you knees, elbows, etc on the ground. Based on that, would it be feasible to attempt to create a standup striking system based on grappling ground striking? surely not.
i'm nobody...i'm nobody. i'm a tramp, a bum, a hobo... a boxcar and a jug of wine... but i'm a straight razor if you get to close to me.
-Charles Manson
I will punch, kick, choke, throw or joint manipulate any nationality equally without predjudice.
- Shonie Carter