Personally, I feel like this is a double-edged sword in a sense. I do think that it is important to protect the long-cherished and preserved Pentecostal distinctives, but I also think that debate and discussion and development with other denominations is also important. The answer is not to isolate ourselves to an echochamber. Not that it would necessarily have the desired effect anyway – even within the denomination there are people with differing opinions. I think a better test of belief and understanding our beliefs is to argue and explain them to others. It's good practice. Not to mention that non-Pentecostals still have thoughts and opinions that can teach us something, and we have knowledge to offer them in turn. That being said, yes, it can compromise the preservation of Pentecostal distinctives. We are easily influenced creatures, and that is why it is so important to continue to seek God's truth in everything.
I do not have a strong opinion on whether or not more frequent ecumenical engagement could help Pentecostals better distinguish between primary and secondary issues of the faith, but realistically, I think it probably would. More discussion leads to more brainstorming, more brainstorming leads to better understanding. I think the biggest implication of this though, may be more and more churches leaning in a non-denominational way rather than adhering to a more established denomination.