Additionally, in this county, there is a rule that if we disturb more than 5000 sf of land, we need to spend about a year in site development review with storm water management, etc.

Do not disturb the tenants.

Assuming you aren't disturbing the commercial tenants' businesses, I don't see a reason why they would leave. 

In a multi-family situation, there can still be requirements regarding pets/esa as in if the dog barks and disturbs other tenants, it can be dealt with.

Ma'am I'm so sorry I didn't mean to disturb you, absolutely I will take you off my list right away.

The biggest piece to closing on something off-market is being able to have an offer presented to avoid the hassle of listing- especially when there are tenants in place that do not want to be disturbed. 

Check your state/local laws for disturbing interior/exterior surfaces/containment/abatement/environmental (particularly if it will ever be a rental).

in affected areas first.Taking out drywall is also fairly easy (big hammer, regular hammer, and flat prybar is about all you need) but is very messy so enclose the work area, wear protection and ventilate it.Note if if this is a pre 1978 house which it looks like it is,   and you plan to rent it,  then legally speaking you must be lead paint certified and follow abatement procedures when removing or disturbing more than six square feet of painted surface in any room. 

Because of this, the regulations around ESAs become tricky....ESA are required to behave well in public, listen to their handlers, and not cause a disturbance.... 

Would having a high number of 'showings' over a sustained period of time cause enough of a disturbance to the jerk tenants to cause them to look for housing elsewhere be 'illegal'?