D&D 5E (2014) Wall of Force Bunker Tactic

I am playing in a meta-apocalyptic Tiamat campaign. It is pretty obvious that Tiamat herself is the last boss, so I try to figure out possible ways to be useful as divination wizard.

The long story short I came up with the following idea. How about to pick Alert feat for the initiatives and use the following combo:
1. Use simulacrum on myself twice.
2. Create a bunker of walls of Force in my turn, where there's only a small opening (between the walls) to hit.
3. Use of divination d20s three times.

Does it sound legitimate tactic? Even if there are casters around I would have had enough counterspells to prevent them of doing so.

Edit: Simulacrum would have been casted prior the combat obviously!

You can only have one Simulacrum at a time.

I used a Wall of Force bunker against Imryth in SKT. Worked so-so, since Imryth could see it and knew where the opening was. My PC skirted around it a bit to cast spells but was seen as a major threat and chased - good thing for Dimension Door!

Depending on the DM ruling, cone breath weapons can flow around obstructions as long as there is an opening within the cone's area.