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In the opening of your statement it kind of sounds like what mustang was referencing, where you might want to use a second gmail account at the Play Store. In that case you could add an account to your Play Store and access both sets of apps the way he described. However, at the end it sounds like you want get rid of your current gmail account in lieu of a new account and keep your apps or change your email in all of your apps without having to go into each one one-by-one. For clarity which of these is the case?
For either of the latter, it doesn't matter which because neither would be possible. If your intention is to change gmail addresses and leave the original account and still have it refer to the data of the previous account you will have to start all over because gmail does not allow changing or editing the address of an account. For example you have a bunch of photos saved to your Google Photos account, marco01@gmail, and you want an address marco02@gmail to also refer to this same Photos account, you could not. You can share the photos from one to the other but they will be separate accounts sharing images back and forth but could not considered the same account.
Likewise if you are just trying to change your registered email for apps you've used as marco01 to marco02, there is no one click or simple method to just change everything to this new email. You would have to painstakingly go into each app or account and change to the new address. There would be no way to get all of your apps to just recognize you are now this new address on their own.
Let me know if this answers your question or if you meant something else so that we can get you the proper information.
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