Incremental increases in block-size will work to avoid the sighash verification attack so long as the blocks fill up not too long after each increase.
(So bumping blocksize up to 2mb or so now should be fine, then again larger later when 2mb blocks are reliably full with TX fee paying transactions.)

Why?
The sighash verification attacker forsakes the TX fees in order to get the coinbase miner subsidy.
Larger full blocks are the swiftest and surest way to move to a TX-fee supported network.
When this occurs, the incentive for this variety of attack goes away and blocksize is no longer limited by this attack vector.

How?
Simple increases (as Satoshi suggested back in 2010), manually introduced as needed, will work just fine.
The main criticism of this is that it is central-banker like activity, however as shown, the need for this manual activity disappears in a finite amount of time in the relatively near future (when bitcoin becomes a fee-supported network).