Maxi Cosi are good for forward facing, and though there is no equivalent but RF only model to calculate with, my rough estimate of the FF score (based on reverse engineering the combined ADAC scores) is good for that seat. Possibly even better than the Trifix - hard to say for certain because it's just an estimate and the Trifix is an old score. But my estimate for the frontal crash score on that seat is only beaten by the Axissfix Air and the Anoris and it's the best price-performance ratio (for FF) on my list.
So personally, I wouldn't replace it anyway :) unless you have another baby in the future to pass it down to.
One of the things that I especially like about Maxi Cosi is their harnesses tend to sit right every time without much fiddling about. Just really well designed. Maxi Cosi FF seats still consistently get good results too. The Titan i-size ones are great if you end up having another DC to pass the spin seat on to.
The Axkid isn't that much more upright than the Maxi Cosi. It's not reclined like the Joie Stages.
I know the line on the car seat groups is that direction makes no difference to car sickness, but I don't really get this because I have seen multiple anecdotes claiming the opposite, and my own personal experience is that sitting backwards will make me start to feel sick almost instantly, so I don't see why this would be different for children. I understand that the claim is that RF only makes car sickness start faster whereas they will still get car sick when FF, just after a delay. But if the delay is 20+ minutes then that covers most of your everyday short drives, so a huge difference in quality of life.
Maybe people who say car sickness isn't important simply haven't experienced it and don't understand what it's like? I still get so anxious before long journeys and I'm sure some of that is related to the travel sickness which was awful when I was younger.