How much would this AES modification improve security? How much would using AES-CTR like 3DES improve security?

Like so (Using a 512-bit key split into two; $K_1$ &amp; $K_2$, and seperate nonces for all stages):


Encrypt plaintext $P$ with key $K_1$
Decrypt ciphertext $C$ with key $K_2$
Encrypt muddled text $M$ with key $K_1$


How much would this improve AES's security? 

EDIT:
After being asked to clarify my idea pseudocode (python like) is available below:



nonces = urandom(16), urandom (16), urandom(16)
key = 'legorooj'*8 # Example purposes, IRL I use Scrypt

msg = 'random message'

data1 = aes_ctr.encrypt(msg, key[:32], nonces[0])
data2 = aes_ctr.decrypt(data1, key[32:], nonces[1])
final_data = aes_ctr.encrypt(data2, key[:32], nonces [2])


Decryption would be the reverse operation of course.
It would not improve security at all.

For AES-CTR mode, encryption and decryption use the same algorithm: generate the key stream using the counter and then XOR the plaintext with it. Because of that, step 1 and 3 would completely cancel each other out, and you would be left with the "decryption" in step 2.

If you'd just use the first two steps then you would actually two independent keystreams. However, as they both rely on the AES algorithm then if the algorithm is broken, your scheme may still be broken as well. This is why usually that kind of construction is created with two algorithms that are rather distinct from each other.

You keep trying to "improve" a cryptographic primitive that is already considered secure. Why not try to improve one of the many problematic schemes? Preferably you would try and first understand the scheme before trying to improve it, like you tried to do for AES-CTR.