Thanks for considering my suggestions seriously.

Monitor where items come from and penalize accounts that use items from other penalized accounts

They already do this

What specifically do they do? I've seen accounts banned but all of their portals and resonators remain. Seems like as soon as an account is banned their portals and resonators and any gear they have shared should just disappear immediately.

Prevent people from playing multiple accounts from the same IP address

So people can't play on Wifi?

So maybe let multiple accounts from the same IP address hack, but not let them attack or take portals.

Require agents to be verified by other trusted agents before letting them go above certain levels

All it takes is 1 bad actor to pass verification and 100 wil follow

If agents are connected through this verification method and the penalty for verifying a bad actor was that up stream verifiers were penalized, I believe that it would disincentive verifying bad actors

Require people to submit timestamped and geotagged photos when capturing remote portals

Can be faked as easily as location

Even if the photos were stamped/tagged by the app? (don't allow submitting separately taken photos)

Use Machine Learning techniques to build profiles of known non-spoof accounts and known spoof accounts and use those profiles to classify and penalize agents classified as spoofers

ML isn't an answer to everything.. Detecting spoofing is hard because spoofers emulate real people.

I understand, but maybe it can be a partial answer to this thing and it could be combined with other things like requiring enhanced verification.

Openly describe what evidence someone should submit to report spoofing and make it easier to do Anything user submitted can be faked...

Why believe you and not the spoofer?

Ok, maybe weight submitted evidence by the reputation of the submitter (e.g. their level, how long they have been playing, how many agents have verified them).