LeaderNoBattle

// Change the return value to be however many maximum battle members you want
Game_Party.prototype.maxBattleMembers = function() {
    return 4;
};

Game_Party.prototype.allBattleMembers = function() {
    return this.allMembers().slice(1, this.maxBattleMembers() + 1);
};

Game_Party.prototype.leader = function() {
    return this.allMembers()[0];
};

Game_Followers.prototype.setup = function() {
    this._data = [];
    for (let i = 0; i < $gameParty.maxBattleMembers(); i++) {
        this._data.push(new Game_Follower(i));
    }
};

Window_MenuStatus.prototype.drawItemImage = function(index) {
    const actor = this.actor(index);
    const rect = this.itemRect(index);
    const width = ImageManager.faceWidth;
    const height = rect.height - 2;
    this.changePaintOpacity(actor.isBattleMember() || actor == $gameParty.leader());
    this.drawActorFace(actor, rect.x + 1, rect.y + 1, width, height);
    this.changePaintOpacity(true);
};

Window_MenuStatus.prototype.actor = function(index) {
    return $gameParty.members()[index + 1];
};

Window_MenuStatus.prototype.maxItems = function() {
    return $gameParty.size() - 1;
};

Window_MenuStatus.prototype.selectLast = function() {
    let index = $gameParty.menuActor().index();
    if (index && index > 0) {
        index--;
    } else {
        index = 0;
    }
    this.smoothSelect(index);
};

Scene_Menu.prototype.onFormationOk = function() {
    let index = this._statusWindow.index();
    let pendingIndex = this._statusWindow.pendingIndex();
    if (pendingIndex >= 0) {
        $gameParty.swapOrder(index + 1, pendingIndex + 1);
        this._statusWindow.setPendingIndex(-1);
        this._statusWindow.redrawItem(index);
    } else {
        this._statusWindow.setPendingIndex(index);
    }
    this._statusWindow.activate();
};