First of all I would have to ask "Why are you changing jobs?" Is it for the money?
Advancement or career path?
Change of environment?
You see, to me if you are worried about the immediate package and the position's opening monetary offer but offers no career path then you should stay were you are currently at until a opening appears that will give you a path upwards. Unfortunately, In my 14 of Human Resources, 80% of the locals make mostly lateral moves and for all the wrong reasons. Don't know if you are local or not but if you can offer a net gain to the company then you shouldn't worry about variable bonuses, they will be there. However, if you are just a salaryman only skating till a better offer comes along, then you probably won't be adding to then net worth of the company and therefore probably won't see a variable bonus either.
Disclaimer: This is only my point of view.
At the end of the day, as an employer I'm going to ask "What can YOU bring to the table" I'll reward you if you are an asset that increases my net worth in the long run.
Call a spade a spade, if you have 12 +2 then tell the prospective employer that. Do you think you will be able to confuse him by telling him 14 months? He's smarter than you are - He owns the business!
Why would anybody undercut a salary? The employer is only concerned with his bottom line, undercutting salary is silly if he would want to keep employees. If something is variable then it could be Zero due to a recession. What you should be more worried about is a portion of your salary being variable as mooted by the government.
A fair package is dependent on the individual, same as market rates. We have too little information regarding the industry and individual. The individual doesn't seem to know too much about his job as he is inquiring about market rates. How long have you been in Ops? Don't you every talk to you counterparts in your competitors industries? How many Jobs have you had in order to gain 4 or 5 years experience. You aren't even sure about how long you have been working?