After literally years, M4 demonstrates WHY SHE IS THE HEROINE and becomes METAL GEAR.

She keeps all her old benefits but has 5 star multipliers and better stats now. This gets even better when Mod3 when she gets a unique that ups her firepower and ALSO gives her armour, so she can kinda tank in a pinch. Her buff tiles are ALSO slightly improved. Her mod 2 skill also tags enemies and enhances the mod skills of other Anti-Rain units.

The big thing however is the desperation mode. At mod2 onward, when 3 or fewer allied dolls are in battle (you can retreat 2 units to force this, or simply deploy her with a partial strength echelon), she pulls out the portable cannon and proceeds to deal hilarious damage that makes grenadiers wet their pants, as huge AoE blasts firing from every dummy. The blasts are kinda 100% accurate (the main hit can never miss, even at night, but the splash damage can. Its weird), and can partly crit (its complicated), and is meant to be a last ditch thing to save a fight under dire circumstances (of course, we instead abuse it). This is however, a doubled edged sword, as her RoF also goes down, so its possible for some enemies to slip by if you havent taken this into account.

Basically, Mod her first. She's pretty much priority #1 for modding.