You might fit three across in a Kadjar - it's worth going to a biggish car seat shop and seeing what they have. Depending on what seat your 3yo is in it might be that you can get away with just changing her seat rather than buying the Multimac.
I don't think the Multimac is terrible - the side impact protection isn't fantastic, and it's quite an old design at this point so it is based more in technology/safety from around 15 years ago than today, the biggest issue being the low rear facing limit, but it was ahead of its time with extended harness up to 12 years and the support leg helps prevent forward movement. It also does what it's designed to do which is avoid children sitting in the crumple zone in a 7-seater. Whether that's still an issue in modern cars, I must admit I don't know, but in terms of cost effective solutions compared with changing a car, it is an option worth weighing up, especially considering many people are comparing with the option of having the eldest child in the middle seat with no car seat and/or if changing the car are needing to change to an older model with less crash prevention/protection features.
It can be a good solution for multiples, especially with a smaller age gap to another child, because of needing several seats of a similar stage for an extended period of time. The main issue is the rear facing limit which is 13kg, that's low these days, many people use rear facing seats up to 18kg or even 25kg.
In terms of fitting three separate seats across, the 25kg rear facing seats are actually among the most compact and flexible because you can fit them further forward or further back on the seats. It doesn't look to me like you'd struggle with front seat space in a Kadjar - possibly in a smaller car. (But you'd struggle for space with 3 kids in a small car whatever the direction of the seats). Remember that the baby seats and some of the cheaper 18kg rear facing seats can only be fitted reclined, so they take up a lot more space. The Swedish type seats are really upright so they don't take up a lot of room at all.
erfmission.com/you-cant-rear-face-in-small-cars-debunking-myths-4/
In terms of 3 across, the most important thing is the shape of the seats and geometry of the seatbelts/isofix points so unfortunately it's just a game of trial and error and there's no real database to consult or anything - just too many possible variations. You could try joining one of the larger UK car seat groups and asking whether anybody has got 3 across in a medium sized car like this, but there are so many combinations of car model/version, children's ages, seat availability/budget/sales etc that it's unlikely you'll find somebody who has the exact same needs as you.