What about doing a long runner instead of a small mat, then placing a mat to the left or right for shoes, plus putting one good wiper at the outside of the front door.

The Water & Dirt Shield mat from Frontgate has a 45" wide option in 59" and 69" lengths plus many others. Or the "Fall Day" Water & Dirt Shield mat is available in 35x82 and 48x72 sizes. Many other Water & Dirt Shield mat patterns are available, and the size selections seem to vary from one to another.

What is outside that door that is where IMO most of the mess should be contained not on that little pad of tile inside.

I use an IKEA indoor-outdoor rug in a flat weave. It's light and easy to shake out, and I can wash it in a standard front-loading machine. 4'4" X 6'5" https://www.ikea.com/ca/en/p/kaerbaek-rug-flatwoven-in-outdoor-multicolor-indoor-outdoor-50319473/

@Patricia Colwell -- outside the door is, well, outside. As in, the place with all the ice and snow in the winter. So it's kinda hard to contain anything there.

@RL Relocation LLC -- thought of that. That might be plan B.

@Partim, that IKEA mat looks like almost perfect dimensions for our space. Thank you! Alas, it seems to be out of stock at every IKEA location across the country. But I'll keep checking.

Also just saw this rug from IKEA that might work for the space, size-wise. Not sure about the colour, though.

I've tried using custom-sized faux sisal rugs from places like Curran Floor. They look much nicer than utility mats and it's great to get exactly the size you want. The only downside is they don't absorb quite as well as the utility mats. So the slush and snow boogers that melt from your shoe and boot treads (after they've warmed up inside your house) sometimes pool on top of the fake sisal. I never noticed the water seeping all the way through, though. I bought the type with the non-slip backing, but options are greater if you have door clearance for a separate pad underneath.

Ikea has other rugs that same size.

Update: We ended up going with a waterhog mat that's 4'x6', so just slightly too small in both dimensions (would've been better if it'd been about 6 inches longer and a foot wider, but alas, they don't make waterhog mats in 5'x6.5').

But I think it works more or less okay. We'll probably replace the light grey boot mat on the left in the photo with a darker black one at some stage. It's not ideal but it'll do.

Thanks for the suggestions, all.

(Now the next step will be to find some sort of privacy window treatments for the sidelight windows... but that's a subject for a different post.)