What you are suggesting is pretty convoluted, and non specific.

The Mercedes on a truck frame has been done numerous times in the past ( it seems that the stacked round headlight fin tail era cars were the most popular )

A few notes. The car will no longer drive like the 2 wd version. Using all MB parts is going to be difficult if you want manual trans and 4 wd.

Do you really need 4 WD? You have a better chance lifting a 2 wd car for ground clearance if you want to retain how the current car drives. RE: push the rear sub frame down, build adapter brackets to move the front suspension down. See also how IFS truck lift kits are done.

If you lift a 4 matic car you will need to push the engine down / lower the oil pan since the front diff is in the oil pan. You will also be limited to an inline 6 as I don't think any 4 matic cars were built as a V8.

If you want to remain with MB parts, the most direct route would be to use a ML frame and drive line.

If you want to use a manual trans, a Ford Ranger / Chevy S10 frame would be better. Dodge Dakota / later Ford Explorer was a larger truck so that might be a better for for a W124 .

Computer control is a non issue if you use everything from the donor truck.

In any event, start looking at track widths for frames that would be a good donor then sort them by wheelbase. Wheel bases can be altered with varying degrees of difficulty.