The London and SE RUS does propose both though, ie 2 tph at 8 car length. The factor left open for discussion sems to be whether to run the second train further north than Watford Jn...
Yes I have no problem with both! I remember reading the RUS and discussing this last time with you

I merely propose one tph running north of Watford to cater for the existing commuter market, the other running south of Clapham likewise. The key market is Watford - Clapham.