Given that you can deploy your canister both locally and on mainnet, did you double check that you actually pass correctly the Gzip file path to Pocket-ic and not inadvertently the path to the Wasm?
That could totally have happened! 
But not this time. The byte size specified in the message, 2,5 mb ca, is the compressed size. BoaEngine I believe take up a lot of that space.
I was under the impression the allowed WASM size for canisters had been raised quite significantly, back in January or there around. See here for instance:
Also, for testing, I tried installing my canister unzipped to ic, 9+ mb, that worked without issue.
https://a4gq6-oaaaa-aaaab-qaa4q-cai.raw.icp0.io/?id=mzakg-qaaaa-aaaal-qjesa-cai
@mraszyk am I misunderstanding something here?