Thanks for the nice script. I needed to change collation on a database which involved ripping out every schema bound object and this came in quite handy with retrusting everything. Thankfully I was able to retrust foreign keys and check constraints with 0 errors. My only suggestion I can think of is to make an easier toggle between fk or ck. It could be as simple as changing your select line to include a commented out line like this:
SELECT '[' + s.name + '].' + '[' + o.name + ']' AS TableName
,i.name AS FKName
FROM sys.foreign_keys i
-- FROM sys.check_constraints i
You could go fancier such as setting a flag that allows either option or both but simply having a commented out line for future reference is nice.