uromastyx philbyi...lots and lots of uromastx philbyi
No, you may not house multiple species together. How many times have you asked about hybridisation and mixing already?
Or, if I got you wrong, multiple plateds together may be fine as long as they'd keep about the same size throughout growth.
I would ditch the grass and go with a monitor specie. Black throats, savannas, and water monitors tend to be docile if frequently worked with. Do some research on those and let me know what you think.
You don't want anything too big, even for that cage if you want to maintain the grass substrate. I would recomend 2.3 Plated Lizards. I used to maintain a group in a large outdoor cage and they were so interesting to watch.
Whatever you get though I would HIGHLY discourage you from taking out for field trips to the LFS. This is a good way to injure and stress your animals and at the very least, risk exposing them to pathogens that could infect your entire herp collection.
yeah i learned the hard way to take your reptiles out my 6 foot python was sweet as could be at home but i decided to take her down the strip because a lot of people do it and she got super stressed and bit me not too fun but yeah like everyone else said i would go with a monitor just be careful they are escape artists good luck in whatever you choose!