What I find strange from the client is they want it on a 2055 form - am I correct that there would be no interior inspection of an AS repaired value appraisal?. That alone is the reason to turn it down imo.
The lack of close comps in itself is not a great reason to turn an assignment down, though we are independent and can turn down an assignment for any reason. Feeling uncomfortable is a good reason - as you have only done five reports, do you have a mentor, or are you on your own? It's a tough dilemma as to how you get experience without stretching yourself on an assignment. Of course, people here can give advice, but we do not see the property - good luck on your next assignment, and know that even we long-time appraisers are still learning.