Scott is way ahead of both Robbo and Pek as backup LHP so moving him to TH would be detrimental imo. I have a lot of time for Paul Alo-Emile at TH and think he will make the grade to backup Kepu. Laurie Weeks is also another with promise.
I agree I think Sio is still our first choice bench LH. I know the plan was to develop him as a THP, but I suspect that Link sees him as a LHP first and foremost.
For the RWC link seems to have two options:-
1) use one of his current LHPs as a 3rd choice TH (i.e. Sio); or
2) take a 3rd genuine THP.
Re option 2 above, the cupboard is pretty bare. Ryan has fallen out of favour for good reason - he wont make it. Weeks seem ok but yet to be truly tested and is quite limited around the ground - his absence during the RC means he's probably unlikely. Alo-Emile is perhaps a smokie, has been dominating at TH in the NRC. he'd have to have a massive Super season and he's currently stuck behind weeks at the Rebels - 2016 might be more realistics.
Looking at those options I'd probably prefer to see Sio given some time at TH on the EOYT and make him our TH/LH prop for the RWC.