As long as it's generally similar to the right scale, it's alright. I'm fine with having the 2007 Ratchet, Ironhide and Jazz with the MPM figures since they're at least generally close.
Scale, literally, is the very thing that cohesively connects my enitre collection. I like to showcase similar iconic characters in various scales, mainly MP, G1, and WST for enhanced nostalgia factor.
Great pics, love how you set them up using their scale as well. Bravo
For me as a collector, scale is extremely important. Without scale my collecting limits would have no boundaries. And boundaries are needed at this time especially when prices are starting to get insane when it comes to collecting official and 3P MPs.
I want Hasbro to release a Deluxe class figure named "Scale" and have his bio mention that because of his unpredictable mass shifting, he's the least important contributor to the war.