Here is a custom-made scenario I wrote recently. Comments will be welcome!

SITUATION
1947, somewhere in Europe... The enemy is about to launch an experimental missile from a hidden base towards your HQ... A special force has been dropped over the area. You must stop the launch!

DEPLOYMENT
Defenders deploy on squa res marked as "D", and begin the game deployed. At least one unit must be deployed on the outer perimeter, outside the base.

After that, Attackers deploy FROM squares marked as "A"

There are two anti-tank traps and two ammo crates for this mission.

NOTE: if using the Revised Core Set maps, treat all squares as "clear"

AVAILABLE FORCES
130 AP per side (contents of the Core Set).

OBJECTIVES
Attackers: you must lead an infantry unit to the objective square and deactivate the missile.
Defenders: Hold the position for 8 turns. After that, the missile will launch.

SPECIAL RULES
Stop the Launch: To deactivate the missile an infantry unit must be on the objective square and spend an SKILL action to deactivate and destroy the missile controls.

We are under attack!: the base perimeter is mined. On the first turn that any attacker unit enters play roll a dice. On a blank, nothing happens. On a HIT, a mine explodes. Nothing happens to the attacking unit, but all defenders are now alerted and can be activated from now on. If alarm does not sound on turn 1, defenders can act normally starting from turn two.

Nice scenario, I really like the "alert" mechanic you posted; nice job making it a 3x3 tile one too.

I will have to give this a shot soon but would be interested to hear how it has played out for yourself in the meantime.

On a random side note; I had created a similar scenario (different map layout of course) for when we introduced the Allied Heavy Walker where the Allies had to defend its construction till turn 4 and then got it for 'free' which ended up hilarously bad for the Axis (myself) having 20 dice rolled against my Armor 2 infantry WITH sustained fire.