It is feasible, but one should be careful with picking a part.
As a course of action, I'd recommend the following:
Filter converters by output voltage. Fixed output voltage will make the circuit simpler, and 12V is a standard voltage, you should have plenty of choice with fixed parts.
Filter by maximum output current (sustained), you want something with overhead, no need to push things to the limit. Over 3A output should work, but no need to shy away from 5A converters. Make sure the converter will have no problem supplying the necessary voltage when the device is idle - low output currents can sometimes be a problem for converters. You should measure minimum current consumption ideally as well and find that current on the efficiency graph of the converter IC.
Check the capacitance of the battery line. That has to be within the spec of the output capacitance of the voltage converter to make sure things are stable. You don't want any oscillating surprises. And you shouldn't add any capacitance there, because the following circuit expects certain capacitance. You can look up if the next components in the circuit can take different input capacitance, but it seems to me like an unnecessary hastle. Just stay within existing specs (if possible).
Check the efficiency of the voltage converter at the expected currents to make sure heat is not going to be a problem. It shouldn't be, but it's not a reason to ignore that. The chip must have thermal resistance rating (C/W degrees C per watt) and efficiency percentage. From that you can calculate power losses in the IC and how hot it can get. +20 (to ambient) degrees should be acceptable, just remember, the chip is probably going to be in enclosed space and with other warm components, so its ambient temperature is not your room temperature. Temperature affects efficiency as well. So don't skip this step. It's not something you can precisely measure (because ambient temperature is hard to estimate), but you should do some napkin math and it should look safe by a good margin.
Of course, you need to make sure the converter can handle peak currents (which are unknown, I take it? Nothing follows from 12V battery spec), you don't want to trip the ICs overcurrent protection. You can always go for higher output current part - again, as low as low currents won't be a problem.
