So far, i see that there are come some codes making the sidechain projects difficult to implement.
Yep. If you want more information you can read these sources:
The Drivechain project - original documents by Paul Sztorc (good read!).
The Drivechain OP Code (general description of the needed opcode)
BIP R10 - Sergio Lerner's proposal for an opcode that counts "ACKs" from miners (in this proposal, the RSK sidechain would be merged-mined by the same miners that mine Bitcoin)
I am not really convinced about the efficency of "semi-centralized" solutions.
"Me too". There are lots of risks, including legal ones (for example, the "Federation" members could get sued for money laundering from a government [or multiple governments], and obliged to give out their keys). I really hope the Drivechain gets implemented, or they find another equivalent decentralized method.