If your are going beyound manufacturers recomendations, it's always a guess if it will work or not. Shimano derailleur spec's all state that the 46 max cassette can only be used in a 1x set up. But a 42 can be used in 2x. So let's keep that 4 tooth gap in mind.
A goat link allows the use of a rear derailleur build for 34 max, with a 42 cog. It simply creates extra distance between the cogs and the upper derailleurwheel. Downsides are that it also creates extra distance on the small cogs, wich can lead to less than perfect shifting, and it lowers the derailleur position, wich can make it hit things in a VM or might cause trouble when using a 20 inch rear wheel.
A Road link does the same thing, but is not as long as the Goat link, it creates extra distance, but less. Check the details here
https://www.wolftoothcomponents.com/collections/derailleurlinks
The links place the jockeywheel further away, alowing bigger cogs, but do nothing for the total capacity.
The front mech does not care much about what happens in the rear. I'd go for a normal compact front road mech version. 34-50 is pretty common. Cause it runs to an idler, there is no problem with the chainline varying high and low on different cogs. In front there will be no problem.
U can find a rear mech, specd to take a 46, that also has lots of capacity. One that does 1x with 46 and 2x with 42. A 47 tooth capacity, with 51 desired has that 4 tooth gap. But i think it is possible to trick the system. U lack 4 tooth, so lets say on the 34 front u only use the cogs from 15 upwards. That will likely work. And the missing gears are close to something u can get using the big ring. Two immediate problems spring to mind. With very little to no tension in the system on cogs smaller than 15, the chain can hang and fall off idlers. A bigger potential problem is that the cage can twist so far backwards the lowest wheel actualy runs higher than the one normaly in the high position. Things can get stuck and then u are in trouble.
Carefull and repeated tuning with chainlenght, playing with the B screw on the rear mech can help finding the best posible option. The shortest posible chain helps in getting away with a bit to much total lenght. But that short chain also has consequenses for the position of the upper Ilderwheel in relation to the cog. Tuning the B screw out positions it further away from the cog, but also leads to more tension on the chain, it twists the derailleur paralelcage downward. That might lead to the chain now maxing out, with no movement left. That's not good. So add a chainlink.
On your VM there is the swingarm motion that also needs to be considered. It does influence chain lenght.
I have used setup's outside the advised range. I always made sure Big-big can be used. If not accidentaly shifting it will highly likely lead to damage, wich includes ripping of the rear mech and directing it between the spokes. If the small-small combo hangs, dangers are less acute. and when the downhill starts, i shift to the big ring anyway.
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