Ability to generate columns
As a web designer, I need to set up grids really fast. Photoshop for instance adapted these guys' method - http://guideguide.me/- and even-though they haven't got it right yet, I still use it a lot.
Ability to generate a Baseline
As for baseline grids ( http://blog.invisionapp.com/design-snack-7-baseline-grids-in-web-ui-design/), I currently maken patterns in photoshop s described in this article. https://www.smashingmagazine.com/2011/11/establishing-your-grid-in-photoshop/. Generating this overlay and enabling snapping to the baseline like in indesign would be something unprecedented ( well maybe aside from a sketch plugin or two )
Generate the baseline and text styles with a modular scale
http://www.modularscale.com/ seeing as the baseline is usually generated together with the text. A combination of these two doesn't seem so crazy i'd reckon.
On a sidenote
When watching the video ( https://affinity.serif.com/en-gb/ui-design-software/ ) about the UI capabilities of this software I find the part about the guides a bit misleading in all honesty. Look at this beautiful grid, creating it however is a bit of hassle, but you can toggle the visibility... Don't get me wrong I'm happy with the product you are supplying, especially at this price, but this feels a tad like false advertisement.