Sidechains can not be done in a trustless manner without a hard fork of the Bitcoin protocol.
really?
Technically speaking as far as I understand a soft fork should suffice to introduce the new needed OPCODE.
Additional OPCODES or other mechanisms need to be introduced to allow validating the SPV proof for the sidechain. It remains to be seen if that will ever happen. Even if it does the SPV proof is significantly larger than the average txn and the potential of multiple sidechains means it is simply not viable under a 1MB block model. There will never be a consensus for SPV proof validation before there is a consensus for a larger block. Honestly there may never be consensus for SPV proof validation anyways but it is at least possible.
So to pin your hopes on sidechains and keeping the 1MB limit is just silly.
So you're saying that since that svp proof needed for ensure the 2 way peg mechanism between the main and the said chains is bigger than the avg txn we need a larger max block size, correct?
But a single SVP proof should suffice to perform hundreds of txns on the side chains (depending on the side chains implementation / design), so maybe the max block size increase could be modelled in a more "gentle" way.
As a side note, did somebody already read/evalute this paper
http://lightning.network/lightning-network-paper-DRAFT-0.5.pdf?