Splitting it like this not only makes the straight draft an issue for release, but it also puts the flash line right down the middle of an aesthetically important area of the bag. Splitting it down the corners means that flash line is much easier to hide, and removes the problem of releasing from a deep draft section as the mould sections will be able to 'twist' away from the component.

The flange at the bottom is not an issue, you lay the sections of mould up separately before bolting them together. For wet lay that is simple, for infusion it means measuring the thickness of the original and calculating the thickness of your reinforcement under vacuum consolidation. Easy to achieve on such a small component.

Alternatively if you aren't confident laying it up as a single piece, then do it as 2 components and bond it together as you say - but that doesn't affect the mould. You only need a 3 piece mould here for sure. Whether you lay the piece up as a single piece or as separate pieces doesn't change that.