I would advise against not using a protected lipo, aka always use a protected lipo. If you must buy something smaller that doesn’t seem to come with a protection circuit, most battery manufacturers can add a protection circuit for you. I would make sure the max discharge currents of the protection circuit are similar to the batteries we use with the Electron & E Series products. You could possibly get away with a slightly lower limit for 3G and LTE though. I believe our batteries currently can handle a continuous 2.7A discharge current before the protection circuit kicks in and opens up the connection and have a discharge voltage cutoff of 3.0V.
In general the PMIC settings should not need to be changed, and the protection circuit on the battery itself is going to offer the most reliable safety mechanism. Depending on the temperature requirements, you might be able to make the charging cycle safer by reducing the cutoff voltage even further than it’s currently set by default at 4.112V.