CoinBase does for USA Canada and other countries you can use their transfer/translate/convert button I beleive (will have to double check the actual word).

This is exactly what made me think this cause I did some conversions In house at coinbse3 when I needed a specific currency and then it stopped working so I did a support ticket to say was my country blacklisted from the free conversions or what and it ended up just being some bug then fixed.

I'm sure if this is profitable it would be a lot of work and probably be less profitable then the 0.1% a trading bot website can get you over time.

I'll make a diagram if k get some time if this doesn't totally explain it (coinbase internal free coin to coin conversions). Thanks. A