Can I circle to a different runway if cleared for an instrument approach without circling minimums? Tom is flying a C172S/G on ILS RWY 31 approach to KSNS. He just established on the localizer at 6000, from the SNS-22 DME Arc. He obtained weather from ATIS, wind 240@20G23, ceiling OVC006, visibility 1 1/2 SM. The wind favors RWY 26 but he notice there is no published circling minimum associated with his current ILS RWY 31 approach. He checked other approaches and found RNAV (GPS) Y RWY 31 @ KSNS has a published circling minimum of 500-1. He thinks since the two approaches are for the same runway and final leg should be similar, he may use the RNAV 500-1 circling minimum and to land on RWY 26. 

X-Wind quick notes: 


Wind angle for RWY 31 is 70˚. 
Crosswind component for Landing on RWY 31 (18~22 knots)
Maximum demonstrated crosswind for C172S is 15 knots


In this case, what should he do? 


A) Continue the ILS RWY 31 straight-in approach and land on RWY 31
B) Advise tower circle south to land on RWY 26. Start to circle upon reaching 500. 
C) Change to RNAV (GPS) Y RWY 31 @ KSNS (approach without vertical guidance), re-intercept final approach course (WIGGL-IVUVY leg) and circling to RWY 26.
C*) Change to LOC/DME RWY 31 @KSNS (load a new approach) and circle at 560 to RWY 26
D) Once he has the airport in sight, cancel IFR and advise tower enter left base for RWY 26
E) Low-approach flying over RWY 31 until reaching 31-26 intersection, turn left and land on RWY 26. 
F) Others, your suggestions.
The only minimums that apply to any approach are those printed on the plate. Doing anything else is being a test pilot. Minimums are charted based on obstacle clearance, descent gradient, distance from the airport, and a variety of other factors.

The appropriate course of action is to either:


land straight in on 31 and attempt to deal with the crosswind. This would be preferred, in my opinion.
go missed and pick up the GPS Y 31 approach and circle to 25. You can't switch approaches once you're cleared. Given the ~1 mile visibility and low ceilings, this would not be ideal.
divert to your alternate if neither of those works. 


Choosing a build-your-own circle with 600' ceilings is reckless - certainly more so than landing with a ~15-20 knot crosswind. There's no guarantee that you'll remain clear of any surface obstacles.