I have this issue as well. Fried chicken being the last time I tried to hold the chicken pieces hot.
I have started to just allow them to cool and eat them at whatever temp they are when I get to them.
I read an article or recipe and I'm not sure where, but the author guaranteed crispy fried food by using his breading technique.
Cannot remember it completely, but I'm pretty sure he used processed (ground up in a food processor), rice in his dredging mix.