All our Phono pre-amps are designed to have an MM cart input type. There is a good reason for that.
There is vast spectrum of MC carts that have a varying output level (high and low) and varying level output impedance.
It virtually impossible to design a great sounding Phono that will sound great with each and every cartridge combination and that will accommodate all the range of those cartridges at the same time.
There is well known notion that compatibility is inversely related to performance. The wider the compatibility the lower is the performance. There is always a choice: It is either high performance (i.e. maximum sound Quality) at the cost of compatibility or high compatibility at the cost of performance. Unfortunately, one cannot have both! Otherwise one ends up with mediocre sound Quality and that is not what we all after if we are looking to maximise the pleasure of music.
If one optimises the sound for one type of cart then the sound becomes compromised for all others as it is counter-intuitive to be optimised for a spectrum.
Therefore, in order to achieve maximum performance one needs to stay ideally with one type of cart.
If you see a Phono that is vastly compatible with everything with a help of switches and/or pots (which amongst other design factors degrade the performance), then I would run away from it as this is the biggest compromise there is. The most compatible device is the most compromised in performance device.
If one thinks in line with that notion, then it makes little sense to design a Phono with maximum compatibility with all MM and MC carts, particularly if one is pursuing the goal of ultimate performance.
Having said that, all low output MC carts work their best with a matching SUT and not with high gain MC phono input or switchable loadings.
The use of a matching SUT, makes all our MM phono inputs compatible with all MC cart use and that solution sounds way better than any maximum compatibility solution.
In the end it is all design choices: one either designs for maximum compatibility or maximum sound quality as one cannot have both in this imperfect world.