General aviation pilot reported ATC instructed them to remain out of the airspace due to congestion when arriving VFR to BFI. The reporter stated their options were limited due to adjacent airports Class B and D airspace and potential traffic.

Narrative

While flying VFR on a cloudless day I contacted the Seattle Boeing Field Tower (BFI) over Kent for a VFR Kent Arrival. The airport was in north flow at the time and I would ordinarily be assigned to straight in for 32L or 32R. Since it was a nice day; the airport was busy and I was instructed to stay out of the Class D airspace and call again in 5 minutes.On the Kent Arrival there are few options available for me to break off the approach since it occupies a narrow window between other Class B and Class D airports. From my initial call I am about 30 seconds from entering the BFI Class D airspace. I can not turn left because I would immediately enter the airspace around SeaTac (SEA). Turning right will take me in the path of straight in aircraft to Renton (RNT) and possibly into the Renton Class D airspace. Fortunately; there were no aircraft going to Renton at that time and I was able to break off and come back about 5 minutes later to complete my approach and landing.I believe that there are safer ways to handle this situation than rejecting the arriving aircraft on the Kent Arrival. The other VFR arrival procedures into BFI (Vashon; Green Lake; and Bellevue Arrivals) all have safe options to break off the approach since they are not as constrained as the Kent Arrival. Controlling airport traffic by limiting arrivals from the other procedures while prioritizing arrivals from Kent would help. If that is not possible; allowing the Kent Arrival traffic to continue while holding their altitude (1100 MSL) and overflying 32R before entering the right pattern for 32R on the crosswind may provide a safer option. Other options my exist that would allow the BFI Tower to better handle Kent Arrival traffic such as earlier reporting of intent by arriving aircraft so that the Tower can accommodate the arrival.