From what I have researched the G10 was a real fighter craft that did exist, now weather HTC modeled it correctly or not is on them, too me it seems like if they had wanted to make a K4 they would have made it, and called it a K4, but its not its a G10, and if what you said is true and it was faster than a g14, then they should have just updated the G10 with the correct engine specs.
Another feature that would be nice of HTC to put in is a information tab on
each aircraft showing the technical specifications of the aircraft on it, engine data etc.
Or put a gondola package on the K4. The MGs caliber on the K4 seems too be in some dispute, from what I've seen most say it had 15mm 151/mgs, I have no idea if its true or not, but it seems like the 109 series is nothing but controversy on what model had what, and from what I've heard, but haven't seen yet but it seems like the Germans kept pretty good records.
IMO all HTC had to do for the 109s was update the exsisting ones and add a few, now what you have to do is decide between the G14 which means more firepower but less speed, or the K4 which is more speed but less firepower, granted tater shooter is power full but gondolas make buff hunting and snap shots easier, not too mention G14 has those big MG ammo bumps on the nose that they seem to have fixed in the G10, if the G10 was faster than it then it should have been remodel too the correct specification.
If the G10 was faster than the G14, however so slightly it should be hear not the G14. I didn't remember them removing any spitfires, in fact they have an extra one unlike the 109s.
As I've mentioned before it has been confusing too find facts on line about the 109s, seems like one person says one model had this or that and another person says there facts are wrong but they dont offer any valid facts of their own, its and interesting odyssey to find the truth lol