@BrettLyder If you want the full functionality of Sage 100 from a remote device, I don't think you have any other options than an rdp to a terminal server, either through a vpn or through a web deployed option like Citrix. However, I would recommend that you examine your salesman's needs before you give up on other apps like iSales100 from XKZero. (This is an iphone app an not appropriate for a Surface. However, there are other options other there as well.)
Also remember that the Surface and Surface Pro do not come with a cellular modem option which means that your mobile sales guys will either have use a USB device or turn the mobile phones into a mobile wifi hotspot. This could leach to technology user challenges if the salespeople are similar to those I typically run into.
BTW, I have a Surface Pro and love it. I'm just trying to think of all the pros and cons.
I would definitely not run the client directly on the Surface unless you will be running on a wifi network connection greater than 50 megabit regardless of the edition of 100. The average cellular connection is significantly less than this. I have never seen this arrangement work well, even with the Advanced edition. At least not since 3.71 days.