A long term tenant came up to me, I think from one of the under market units, and told me she was very stressed by my letter, that they have a community in the building and she hopes nothing will disrupt it.

Multi makes a difference - its not just her place, it's her tenants being disrupted. 

Seems to me it would be better to issue a 3-day Notice to Quit regarding the drugs and disruption of other tenants.  

I would say the pro forma process is prime for disruption 

The work doesn't require relocation, and no utilities will be disrupted.

I would call it “Storage Hacking” remove some walls add a bunch of cages just for storage..Neighbor is out to disrupt self-storage: It's like Airbnb for your stuff https://www.cnbc.com/2019/08/20/neighborcom-is-out-to-disrupt-self-storage-its-like-airbnb-for-stuff.html?

I don't want to disrupt my guests so I think I'll just continue to do that.

Of course this doesn't eliminate the fee paid to the buyers broker.I do believe that eventually someone will come up with a workable system to disrupt the real estate brokerage industry, at least in part.  

How much will it really disrupt in my buying process if I go with the other agent?

If I had the same situation on my own home I'd expect a certain amount of disruption and accomodation to the plumber's schedule - life ain't perfect and in that scenario the plumber's the one in the driving seat.How would that be an 'unreasonable disturbance' when the task is to try and sort out their plumbing problem ?