Yes, balance changes may be geared towards pro-level play, but it still needs to be relatively fun and fair for everyone.
Regarding the overcharge ability at hand, it does really feel like a band-aid, but more importantly, it is highly dependent on a specific Nexus having the energy. When a new Nexus has been built, it is far too tempting to immediately use its energy to Chrono out new Probes from it, and since it’s the closest Nexus (being the same Nexus you’re placing Chrono Boost on), it will use energy from that, meaning it can’t be used to overcharge nearby Shield Batteries anyway. The other thing is that you have to wait for it to charge an additional 25 energy, which may already be too late. Ultimately I don’t think it’s going to work - I’d much rather Chrono a Phoenix or something.
To give my own alternative suggestion, I’d wonder if something like my Sentry energy upgrade might work (allows a Sentry to cast Guardian Shield the moment it warps in). It’s clutching at straws a bit though because that too might be too slow to defend the natural, but might help with defending a third, along with providing more options for build variety:
Honestly, I think the best approach in regards to the PvP Proxy Robo build is to revert the cost of the Robotics Facility back to 200m 100g and the Immortal to 250m 100g (but keep the Warp Prism price the same), hence delaying the proxy slightly and the first Immortal costing slightly more (200 + 250 = 450m compared to 150 + 275 = 425m).