EMIYA (Archer) + Georgias a good idea?

He's okay, but as a rider, he's going to be stealing a lot of the crit stars that you want EMIYA to have. Be aware of that.

As said above, Georgios will most likely absorb all the crit stars EMIYA needs to perform his best. Consider Mashu as an Arts-based tank instead, and if you got your own or a friend support's d'Eon who's a Saber as well who won't steal away the crits.

Better off stacking def/healing with tamamo or mash + waver

My friend, have you considered Jeanne D'arc (not the alter version)?

Unlike Georgios she has no taunt, but thanks to the Ruler class she takes reduced damage from ALL classes save for Berserkers and Avengers, with the latter being an extremely rare class. Also, her NP features a 3 turn defense boost, a 2 turn teamwide auto healing and teamwide invincibility for one turn, which needless to say, is an amazing support even at NP1. Her BAAAQ deck and Arts NP synergizes really well with Emiya for building fast NP bars. Finally, her first skill also gives you crit stars each turn, which again synergizes well with Emiya since she won't be stealing his stars, while Georgios probably will.

Offensively she isn't that great, but that's a minor setback the way I see it. If it's an arts tank you're looking for, I'd say she's a good shot to take, if not your best. Additionally, if you need extra insurance, you can take Mash along as well, although that would greatly reduce your offensive damage. She'd also be a good option in case you don't want/have a Jeanne in your team.

Best of luck!

I second StepOfDeath. Jeanne D'Arc is hands down the best tank in the game and she has an arts deck, so she checks both of the boxes you ask for. While she doesn't have a taunt, her NP will more than make up for that with a 2 turn heal, 1 turn invincibility, and 3 turn defense buff. The second best option would probably be Best Kohai.