In the process of making some more advanced character systems I found it to be way simpler to just code the math than doing all the operator actions. This is the first action I made with the intention of condensing some of the work you need to do in order to compute stats.
It's intended to calculate the natural stats of a character based on their level.
// (c) Copyright HutongGames, LLC 2010-2013. All rights reserved.
using UnityEngine;
namespace HutongGames.PlayMaker.Actions
{
    [ActionCategory(ActionCategory.Math)]
    [Tooltip("Designed to set a stat value based on character level and increase rate per level.")]
    public class StatByLevel : FsmStateAction
    {
		[RequiredField]
        [UIHint(UIHint.Variable)]
        [Tooltip("The final stat variable.")]
        public FsmFloat statVariable;
		[Tooltip("The 'base' starting value of the stat at Level 1.")]
		public FsmFloat statBaseValue;
        [Tooltip("How much the stat increases per level.")]
        public FsmFloat increasePerLevel;
		[UIHint(UIHint.Variable)]
		[Tooltip("Level of the character.")]
		public FsmInt level;
		[UIHint(UIHint.Variable)]
		[Tooltip("Other float variables to add.")]
		public FsmFloat[] otherVariables;
        [Tooltip("Repeat every frame while the state is active.")]
        public bool everyFrame;
        public override void Reset()
        {
            statVariable = null;
			statBaseValue = null;
            increasePerLevel = null;
			level = null;
			otherVariables = null;
            everyFrame = false;
        }
        public override void OnEnter()
        {
            DoStatCalc();
            if (!everyFrame)
            {
                Finish();
            }
        }
        public override void OnUpdate()
        {
            DoStatCalc();
        }
        void DoStatCalc()
        {
			statVariable.Value = (increasePerLevel.Value * level.Value + statBaseValue.Value);
			if (otherVariables.Length > 0)
			{
				for (var i = 0; i < otherVariables.Length; i++)
				{
					statVariable.Value += otherVariables[i].Value;
				}
			}
        }
    }
}