I don't think this is a good idea to say the least. My reasoning is my own personal experience.
I started playing in 2008 and finally when I burnt out in 2013, I quit the game and, literally, didn't log on some of my worlds for full five years. Now, as you can see - I'm back and an active player again and I'll most likely keep on playing for more years to come. Coming back to activity was made easier by the fact I had two surviving high level accounts which I could build upon. I'm very sure there are many out there like me, players who simply got tired of the game and left and who might come back some years down the road. Starting again from scratch is a difficult thing and most older players wouldn't be motivated to do so.
I can understand the logic of this exercise - that there are many dead accounts cluttering up the system, my recommendation would be to delete only the low level accounts, those between 1 and 80, while preserving the higher level ones.