It would be totally different if it were a single family home and my neighbors had issues with him.. but these neighbors are also my tenants and they deserve to enjoy a peaceful, comfortable and safe home. 

We always try to make sure they are happy and enjoying their home.Unfortunately,  we do not do any outside management.

There is a construct in law that is known as peaceable enjoyment. 

We have family there (an Army surgeon and Army supply officer) and they purchased a home and really enjoyed living in El Paso.

We both work too long and hard for the money and don't like spending it, but you do have to enjoy life! 

(I still do D4D I enjoy it) Use the 4 pillars.1.

I like the way you are thinking of ways to make the space enjoyable and functional for a larger number of tenants.

Our biggest challenges are 1) tenant friendly (impossible to increase rents to keep pace with market) 2) High price per door 3) Poor rent to price ratio  If your approach is to gamble on appreciation, Metro Vancouver may be a fit, but I've found better overall returns elsewhere.

And I’ve enjoyed having them all and getting to know them.

In order to promote the tenants ability to quiet enjoyment of the premises you can put simple rules and regulations in place.