Think of it like this for solar. If you add more solar plants, the supply during non peak hours would be huge 300 GW of Solar for 4 hours would mean 1200 GWh of Energy. Parts of which will get consumed and parts of which will be in demand in non peak hours.
If you add more BESS ( BESS is capex heavy, 100 - 150 USD per kWh for a life of 10 years . Also assuming it is lithium ion cathode ), definitely the prices would stabilize and maybe some bilateral contacts may also take place. But I feel a bulk of volume will go via the exchanges. The arbitrage might be lower but BESS is the only way to reduce spikes in demand and supply. With RE you have both spikes in demand and supply.
I feel we will see more BESS as rent coming up in central places which will be handled by a separate operator for example JSW. This way the BESS operator utilization would be high as they would collect and store from multiple locations and supply during peak hours.
I also feel that due to non enforcement of RPO and no penal provisions, Utilities are not prioritizing the RE as a % of overall energy mix. With regulation this might change and the demand at peak hours can take the price further up.
A subsidiary of HEG is a good ancillary play on BESS. You can read more on the thread. Other beneficiaries are lithium ion cell / module manufacturers like Amara raja and Exide . BMS players like Shivalik, PML ( shunts ) . Capacitors - XPRO etc. Maybe some cooling system suppliers and Inverter suppliers like Siemen / ABB etc.
Disc : I am not a power / Power grid expert. In case there is someone in this thread please add / correct my assumptions.