What are you vaping with now that you think a mech mod is "going up"?
You might just find the opposite is true. With limited voltage you will be unable to heat some coil builds fast enough to use them. For example, a dual coil .28ga 1ohm build may take 3-4 seconds of firing before the coil is hot enough to really start producing vapor. You've got to not only know how to build coils, you've got to know how to limit the amount of metal in your coils so they work well on the voltage limitations of the mech mod. You can't just turn up the power if it doesn't heat up fast enough or well enough for you.
For example, this .7ohm coil would NEVER work in a single battery mech mod. It takes about 8.4V to make it work. The best you'll get out of a mech is 4.2V when the battery is fresh off the charger.