Could you add a few features or rather smooth out the process that would help those in pre-press?
Ex: Placing a 1200 dpi TIFF file as the original printing size and not defaulting to 300 dpi. When this happens it changes the print size of the image based on 300 dpi. I can change it to 1200 dpi and that brings it back to original size : but that happens because I know it was 1200 dpi.
In Designer and Publisher to add another color model: one with palettes , so that we can have true line art images, called bitmap images ( either pixel on or off - and corresponding to 1 color)
In Publisher: add to the spread options a feature to have printer spreads instead of reader spreads. I know most print servers and copiers can automatically paginate a booklet but sometimes I need the pdf already paginated. Ex: Goes to a offset press - 1 spread of 1 side per plate and then the press run. Collated into a booklet on an Duplo booklet maker. One and Two color offset presses could use this since the RIP servers that produce the printing plates do not paginate this for you.
In Publisher: when going to print dialog; have options for separations, or/and print to a postscript file with those options.
Note: Affinity has done a great job and now has a real publishing presence. Suggestion: Instead of adding a lot more designing features make prepress better. Pre-Press folks take someones file and prepares it to work on offset, digital, or letterpress. I do all three.