I think the Spare morph would be even more effective (or at least cooler) if it were built directly into the main morph, as a sort of body escape pod.
Instead of being a separate unit that the CS is plugged into, the Spare is instead located inside the morph's body, around its brain or cyberbrain. The brain is connected to the rest of the body via connectors that feed through the Spare's body, allowing the user to switch between controlling the body and the Spare. A hatch allows the Spare to quickly escape the body, carrying the brain or cyberbrain with it. This could theoretically work with any morph as long as the Spare is large enough to contain its brain or cyberbrain.
This has some tactical advantages, and honestly I just think it's a cool idea with a lot of potential. I like the idea of playing a big, hulking Synthmorph or other morph which turns out to be piloted by a tiny robot that pops out of its head.
And you have even more potential with a macabre variant of the Escape Pod- the Hijacker. The Hijacker is built to burrow into morphs and take control of them- I'm thinking that there's an Exsurgent version that can jack biomorphs, but normal ones only work on Synths and Pods. It would make a great morph for a unique, threatening antagonist or group of antagonists, and particularly devious players might try to capture one of these and reverse-engineer it.
23 Liminal Blossom Punctures the Heart of the Unrepentant, Deliciously