The problem I have and had with the Bf109G-10 is that its service entry was actually after the service entry of the Bf109K-4. As such, it doesn't fill any gaps.
What we actually need is a Bf109G-6/AS or Bf109G-14/AS.
It could work that way too.
The Bf109G-14/AS (or /ASM; indicating that it is mounted with a DB605ASM engine) is quoted at 348 mph at seal level, and 423 mph at 25,000 ft. Although the G-10 is mounted with a DB605D, the performance is very comparable. Also, considering the K-4 tops out in max speed at 22k, the higher FTH is a clear indicator of the high-alt /AS engine.
Therefore, I'd expect the Bf109G-14/AS could very closely stand in for the G-10 when required to do so - thus, it is a good choice.