The Oerlikon Gyrobus worked in a similar fashion, although 3-phase, and without the chemical battery element. Intermittent rail electric systems are not exactly new. Another idea involved continuous third-rail on adverse gradients, with stored energy used on the level, and regeneration when running downhill. It isn't the technology that's lacking, it's the impetus. What we need is a massive oil embargo. We would have it solved within the year.
ANY form of temporary connection would suffice, including a jumper cable. The original Parry cars had a sliding side contact at stops, to recharge the flywheel. My proposal to return MET services to Aylesbury includes (among other things) recharging of accumulators during layover.
The incline into King William Street was designed for cable traction, where wheelslip isn't a factor. A similar legacy are the steep gradients on the South Devon Railway, originally designed for atmospheric working.