Yes it would work. I would rather do that than put in all mix straight away, since its pretty heavy on nutes. However i would rather mix the all mix and light mix(or replace this with coco) along with some clay pebbles or perlite for aeration and not repot.
As matty mentioned repotting autos is fine, but autos dont leave as much room for mistakes than photos, since if you fuck up a bit with a photo, you can just veg it a bit more for it to recover, but autos just flower when they are ready for it. Thats why you need to be careful not to keep it in too small pot at the beginning for too long if you plan to repot. If you really know what you are doing, you might even be able to do some air pruning and have better results from repotting than no repotting. But if that is not your aim, then its easiest and most stress free to just plant it straight away in final pot. If you repot too late, then it wont have time to grow proper roots, because root development slows down a lot in flowering. It still grows roots in beginning of flowering but if you give it like 2 weeks from that, then it doesent help so much to repot anymore, other than not having to water as often.
If you do repot, use myco's and some other stuff to help with the transition.
Root size and plant size are directly correlated(ofc there are also other factors) and if you stunt the root development, you stunt the whole plant.