I was thinking of another engine coming in and releasing an engine at the stops. But the sidings are way too short anyway.

DC or DCC?   

Must admit I assumed DCC with all tracks live, given that the original diagram includes the siding feeds and the isolating joiners on frog Vs indicates electrofrog points.

Yes it could all be done with a single feed on the left using blade contact only and no IRJs, but not as reliable perhaps.

Sorry, should have mentioned it'll be a goods yard and DC. The extra feeds, as previously stated, are more for robustness, although they could be used in the future for DCC.