If I understand what you are asking, you want to attach a ramp to the house, (at the same level as the door), which would go to the rim of the spa. Thus you would be stepping into the spa as if it was sunken into the ground?
I'm no expert, but I think most here would recommend against this type of setup, as it is too easy to fall into the tub and hurt yourself.
I would compromise and have the ramp level the same as the entrance/cool-down seat inside the tub. That way you would walk up to the tub, sit down on the side, and swing your legs over into the cool down seat.
Don't forget to have them apply a paint/sand mixture on the walkway of the ramp, for extra skid resistance.