Does it make sense to rely on tax implications / benefits to justify this as a good investment?

Huge benefit. 

Think whether this ADU makes sense financially for you, and should you also get tax benefits, then it's a nice bonus.

I'd add index funds, reits, equity markets have benefit (and overhead) of greater regulatory oversight/compliance providing some protection/assurance for shareholders.

Their return from appreciation would have no benefit of leverage.  

My spouse doesn’t love having a tenant and sharing walls with someone but can see the benefits.

However, this requires careful planning and adherence to 1031 rules.Holding and Renting Units:Retained Units: For the units you retain (one for your business and one for rental income), you will continue to benefit from rental income and potential appreciation.Depreciation: You can continue to depreciate the retained units, which provides additional tax benefits by offsetting rental income.With these considerations, this approach allows you to leverage the benefits of a 1031 exchange while maximizing the potential of your investment in the commercial property.

They often just have convenience fees and other added charges which isn't always to the owner's benefit.

They typically involve two agreements: a lease agreement that outlines the terms of the lease (rent, responsibilities, etc.) and an option agreement that grants the tenant the right (but not the obligation) to purchase the property within a specified period at a predetermined price.Negotiation Power: Lease options can be attractive to tenants who may want to secure a property for their business while potentially benefiting from any appreciation in property value.

When you purchase a property, those benefits don't necessarily come with it.