Pruning of the blockchain is apparently technically plausible for Bitcoin and some apparently effort has been applied investigating that. Will probably be less efficient than the mini blockchain.
It is more than plausible, it is explained in the original paper. On the surface less efficient if addresses are reused (which is often not recommended), but not dramatically so. Both end up with block headers plus UTXO.
Cryptonite has some other nice features though. The 10 year reward halving schedule is unusual, perhaps valuable, and will never be adopted by Bitcoin. At least it pushes very-low-reward issues out several decades.