Design Heatproof parachutes..................
That is exactly what a ballute is, a hypersonic heat resistant balloon parachute...aka ballute. All previous attempts at hypersonic ring parachutes have failed. However inflatable heat shields, inflatable drag devices and ballutes have been successful.
If SpaceX wanted too they could make the second stage recovery a option for low earth orbit missions by sacrificing some payload it would open the lower end of the market for them and crush every other small sat launcher since they would only need to pay for fuel and recovery ops plus referb. Recently they flew a F9 first stage nine days after it landed , think about that they landed a booster and 9 days later it was launched again that includes referb, second stage and payload integration plus preflight testing all in 9 days.
Falcon Heavy can put 28,000+ Kg into LEO recovering all three boosters so much mass even a hit of 4,000kg is 24,000Kg plenty for a disposable kick stage for GTO or GEO missions in the ten tonne class. The other choice is go to GTO with the second stage like normal take the payload hit of 4T and keep just enough residual fuel mass to lower perigee down to sub 200Km then use a lifting drag device just like the ones from the group above to pull you down into LEO it’s identical to aerocapture ops once low enough you start entry decent and landing using the same drag ballute targeting the Florida Atlantic coast, there is a nice long runway where the shuttle used to land...You only need a few hundred feet of it for the skids under the parafoil guided stage 2 halt it.