Regarding a card reader, you can get one that works via USB, my brother Richard showed me a cool one he got (forget where, he might remember) that took a micro SD card (slides right into the USB plug).
That should work well for transferring files, less so for regular use (may stick out some).
My ASUS tablet has an SD card reader and I use it frequently to get videos off the GoPro cards. But it did did not have a USB port, does have a micro USB plug (used for power as well) and I bought a cable to plug USB in, mostly used for a USB flash drive (again off loading videos or other files). Since it is not windows it did not work with a USB hard drive (or was taking too long trying to scan it for content).
This tablet also had HDMI (but a mini/micro version, I bought a cable and have used to plug into TV for various uses). It has been a great tool for MC travel and I'll continue to use it. (Don't need/use Basecamp on the road. If I need custom routes I'll create them manually in my GPS.)
One lesson I learned was to do a bit more research, this tablet came recommended by a friend and has been a great tool. But I found after buying it that the version of Chrome cannot be updated. That has not presented any problems in the 5+ years I've been using it, it has the apps I need, I can still get on most websites and such.
