Several things you need to consider.
1) Size and weight. On a bike, something that big is going to act like a sail. Also, the heavier a mounted item the more it is going to vibrate rendering it unreadable/unusable.
2) Screen type. In all likelihood, the screen of a tablet will act like a mirror when used during daylight hours especially on clear sunny days. If you cannot see the screen, what is the point in having it mounted to the bike?
3) Dust and dirt deterrance. Unless you have a high end sleeve to protect the ports and screen, it is going to make the item prone to getting damaged. Apple is usually always the first in line to deny any warranty claims to their customers, so keep that in mind. Also, even if you did have a sleeve it would likely no longer fit the holder such as the one linked in the first post.
4)Useability. With something that big mounted, it is likely going to interfere. Most likely it is going to obscure most if not all of your instruments. Also, it may cause interference when turning at full lock.
5) Battery anxiety. Screens are the biggest consumer of mobile devices. The larger the screen, the more battery power needed, the heavier the weight, etc. Since you are planning on using this presumably for work purposes, you need to determine if the device can last a full shift + at least 2-3 extra hours screen lit at full brightness nonstop on a daily basis. Yes, the MP3 does have a USB charge port but again then you will be exposing the device to dirt/dust & water making it vulnerable although Apple will be more than happy to sell you a brand new unit.
6) Theft deterrance. You will need to invest in the necessary hardware to prevent your device from getting stolen. Mounting something as big as a 13inch tablet to a bike is akin to putting a neon "STEAL ME" sign on the bike.
FWIW, I've tried the cell phone solutions but I keep coming back to my hard mounted TomTom. Why? It fits perfectly in the center valley of the handle bars and thus no vibration. It is fully supported by Piaggio since they sell the wire harness and mounting hardware to eliminate any hacking of the vehicle electrical system. Also, the system turns off automatically when the ignition is shut off. The most important 4 reasons? The TomTom has a solar cap to eliminate solar glare. Secondly, it has a perfectly matte screen to ensure it remains readable under all conditions. 3rd, the system is watertight. I've used mine in rain, snow and ice for over 5 years without any trouble since the GPS is powered through the gold finger contacts on the back of the GPS (no cable connection) as shown in the 1st pic). Fourth, the screen can be operated with gloves on. I cannot stress the importance of this last item which lacks on all phones/tables or other non motorcycle related touch devices.
Here is a sample pic of my TomTom mounted on my MP3 taken with the sun directly hitting the GPS & instrumentation. As you can see, the screen remains perfectly legible despite being a very sunny day where even the instrumentation is having trouble with sun glare.