You would be taking a car with excellent ride & handling characteristics and compromising them unless you spent a lot of money, and even then you might still be left with compromised balance of comfort & handling.

As you change the spring constant of the springs, you will be changing the balance of damping in the shocks and the travel of the springs as a function of applied load. This should adversely affect handling on uneven 'ratty' roads as the damping will not be optimized.

Back to the geometry question, caster & camber in the front is adjusted by means of eccentrics on the inner pivots of the lower control arms. Unfortunately, since these are both affected, it's hard to analyze the available range of correction. The service manual has a nomograph to show the interplay of these two aspects, but you'd have to also know what your current settings are as well as the position of all 4 eccentrics, etc. . . . Hard problem for analysis. At least it's adjustable in the front.

When we go to the back, the situation in the rear trailing arms is not as easy. The only real way to adjust camber is the spring/spring pad stack height and the position of the differential mount relative to the body. As you reduce the spring/spring pad stack height, you will increase the negative camber. To mitigate this with the diff mount position, the diff mount would need to move up into the floor/frame of the car. That's going to be hard to do. I'll throw in one other little known tweak that is technically available. These are eccentric bushings for the rear trailing arms. These are only available from MB (what other mfr would even offer such a thing?!). These are used to correct toe in the rear axle predominantly for a car that's been hit & tweaked a bit. The eccentricity of the bushings is only 1.5mm; this is so negligible compared to the ride height change that it is essentially useless as a camber tweak. The bushings are also > $50 each.

Given all these disclaimers, if you still want to figure out how big the changes would be, you can get under the car and measure the three sides of the triangle of the rear trailing arm. Two vertices are the pivot points where the bushings are and the third is the center of the hub. I have done this to analyze a correction for toe in and made a 3d drawing. The lengths of the triangle sides are:17.38, 24.51, 21.11 in inches. I analyzed the camber effect of a 1" drop in ride height, i.e. shorter spring stack. This caused a -2.7° change in camber which is pretty sizable. I would think that this represents a maximum realistic change to ride height.

The change in the front would be even more as the triangle of the lower control arm is shorter, but it also has eccentrics where you could adjust this somewhat.

Two other things to check in the back are the current rear wheel camber. You can certainly eyeball this looking at the car from the rear and spot 1° of pos or neg camber easily. The 2nd thing to check is the state of the diff mount. As these get old, the center piece can become detached from the frame allowing the diff to drop, which raises the wheels and causes significant negative camber, etc. This seems unlikely in you case, because if you had this, the car would already look low in the back.