By far the easiest is to use id and not worry about it. If it's that important, I would suggest leaving id as-is and either adding a new field or using a virtual field that does a simple hash. I've seen hashes as simple as multiplying by a small prime number like 1007.
So:
Field('bigid', 'integer')
db.mytable.bigid.default = lambda r: r.id * 1007
And then always use bigid.
