You have to pass quality checks and minimum display requirements, updatebility, etc. for which the Eurosim can be a real pain in the neck. Some of them still use XP which, while being OK in and of itself does not allow for the updated drivers you need if you change motherboards. You will have to budget in the cost of X-plane (the professional version) which is now the software of choice. Both MS and Prepar3d have limitations that are limiting development of new aircraft and scenery. Also, the original Eurosims used very obscure Panasonic projectors and you will also need new potentiometers. These can be bought for a couple of Euros but the manufacturer will charge a fortune.
The Flyit is certified for FAA use. I know of a secondhand eurosim if you want to PM me.
phil