I make “instant” pho somewhat regularly.  The secret is keeping a homemade pho seasoning mix on hand.  As long as you have that, noodles, some kind of greens, and some protein source that can be thinly sliced (I like tempeh) you’re well on your way to a fresh and delicious bowl of soup.  I make my own mix based on ingredients in pho cubes from an Asian grocery store.  I’ll post a recipe once I’m done experimenting with the ratios.  It’s tough work sampling so many bowls of pho!