It is impossible. For example, let's assume that k1=2, k2=3. Then, if you take Q=GenesisPubKey, you would have:

2*halfGenesisPubKey=GenesisPubKey
3*oneThirdOfGenesisPubKey=GenesisPubKey
genesisPrivKey*G=GenesisPubKey

Finding "genesisPrivKey" is impossible in this case, the same for any other public key. If it would be possible, then ECDSA would be gone instantly.