Ok, let me first say that the MixPre II is a fantastic mobile recorder: nice analog limiters, 32bit float audio, good haptics, sturdy built...a great product.
The Mixpre’s just have one flaw: Powermanagement. Forget about Alkaline batteries, the Mixpre‘s eat them for breakfast: between your first coffee and your cereals the batteries will be gone. What about USB-C then? Well, this is very good to have. But you cannot rely on a flimsy USB-C connection for live recordings as the cable will come off too easily.
So, then we have the MX L-mount. This is a reliable, professional solution which depending on the NPF batteries in use can last you a whole day of shooting/recording. But the battery mount in essence is a lighweight piece of plastic which does not easily connect with the Mixpre’s. Each time I am removing it I am concerned the brackets come off. A price of €25 for this thing would be fair and would still give Sound Devices and its resellers a healthy margin. A price of €50 would be steep. A price >€100 is just excessive. This is where the Zoom F6 has a competitive edge!