There should already be a delay between the indoor fan and the heat pump compressor. The indoor fan should always start first, then the pressure switch should make - proving airflow, then your compressor should be allowed to run. I would not recommend starting the compressor first, you would have to jump out the pressure switch. The airflow proving device is there so you don't freeze the evaporator coil like a block of ice (seen it happen a few times). I'm really surprised the compressor wouldn't start with that size genny. The startup amperage must be too great, I'm sure the RLA (run load amps) is within range unless its a huge heat pump. What gauge wire is installed between the genny and the transfer switch and from the transfer switch and the outdoor unit? Also what is the generator rated for in output amps and what is the FLA (full load amps) of the outdoor unit. I'm sure you sized it right, right?