A few good articles are up on the topics of collateral and clearing:
This article on Bloomberg highlights the fact that banks will be prepared to use the cheapest collateral possible, regardless of quality. That could of course have quite an impact on the objective of “systemic risk reduction”.
Similarly this article in IFR looks at the looming rules on Initial Margin on uncleared trades. If widely applied, it could discourage hedging by end users, thus also negating the desired system risk reduction of the rules.
Finally, this article in The Trade talks of the challenges of clearing less liquid instruments. It highlights the fact that if ESMA were to push CCPs to clear less liquid instruments, the risk to the CCPs will go up, hence causing clearing members to possibly worry about the riskiness of the CCP. the recent proposal in consultation indicates that ESMA will focus on requiring clearing for liquid instruments.