Not very encouraging to imagine ChatGPT to be the first earthling to reach another star system, but that's an option we'll have to keep on the table, at least for the time being...
The universe really doesn't want ChatGPT!
It is fair to say, that given space travel tech improves slowly relative to AI, but the distance to be travelled is so great that any rocketry (or other means) improvements will quickly pass previous launches, the first intelligence from Earth that makes it to another system will be superintelligence many orders of magnitude smarter than we can probably imagine.
It would work better for smaller, unmanned craft, especially when you consider g force limitations
NPP is only theoretical, and still has major problems such as finding a material that can withstand a nuclear detonation at point blank range. Mass drivers have been proven to work, albeit at a smaller scale
Of course, depending on how much oil you consume for each shot, you will degrade your effective specific impulse - I'm not sure by how much though.
The other issue which you can't really get around is thermal, that plate is going to get hot so you'll have to give it time to radiate heat away between shots. This may be less of a concern for an interstellar Orion since the travel times are so long anyway, low average thrust may not matter too much.