I've been trying to make a good file with Bel Kingdom for ages, and it's wasn't until I got thrashed by a file very similar to this one that I saw where I had been going wrong.
It's versatile, has great synergy and ability to rush along with a great end in Ainhazard.
The Guardian provides an excellent alternative to grims
You have to watch SP in case Ainhazard conks out.
You don't even need to use Ainhazard's action skill as he is buffed plenty by other units.
If something disastrous does happen to Ainhazard you can always fall back on remaining dragons and riders.
The file is UD atm, and when Dyson gets dump down I will probably try to squeeze him in somewhere. Along with a Rapid Growth to help keep Ainhazard on. Allind and Bel Light Cav are other possibles.