To answer the OP, anything is possible. Yes, technically, has no original members.
The statement that "Petrucci is irreplaceable" is just opinion, and might ruin the DT experience for you personally, but there is absolutely no reason that he could not be replaced, should he (or more correctly, the group that owns the name) allows it to happen.
I have no doubt that Gene Simmons has an angle that involves money, but Paul has said the same thing, and I think - at least in some of the interviews - that it was meant more existentially. That "KISS" the entity was bigger than any one person, and whether you like the various incarnations or not, it IS. They have, at various times, played with replacements for ALL FOUR members, and survived.
It's all down to the ownership of the name and the authority of the members that control that name. And it need not be a band member. Let's say I was the manager of "Yes", and let's say Chris Squire was the sole owner of the name. If as part of the estate planning process, he transferred that name to me upon his death, I could, legally, float an official version of "Yes", and pick five new members to comprise that band. Whether it would sell music, whether it would attract fans, whether it would be credible, these are all legit questions, but none of them actually decide whether it's possible or not.
Except in the event that one member - Steve Harris (Maiden), David Coverdale (Whitesnake), Neal Schon (Journey) likely fall into this group - owns the name and controls the entity, the idea that a band member is "irreplaceable" is largely opinion, and largely about taste and preference. For example, to me, Sabbath isn't Ozzy or Iommi (though also Iommi) but Geezer. I saw Sabbath multiple times with Geezer and without, and it's a different band without him, and an inferior band if you ask me in my humble opinion. I am a die-hard Kiss fan, and frankly, having seen the band multiple times with and without Peter Criss, he's a liability. It's a better, truer Kiss WITH Eric Singer in the band than with Peter Criss, if you ask me in my humble opinion. I understand and respect that others see different, but at the end of the day, our opinions are meaningless, and only Tony and Ozzy can decide (for Sabbath) and Paul and Gene (for Kiss). We can only choose not to go or not to buy.