For this scenario, there are definitely two approaches!
First one is the "Per Structured Engineering" way of looking at it. By design default, the load calcs designate a service ampacity size, which would need to be met - so as far as "The Blind Lady Of EE" (like the blind justice lady), the service would require upgrading.
Second approach is the "Real Life" aspect!
Since there is only one person working on stuff, chances are two or more heavy load machines will not be driving out at near rated horsepower all the time. Even if this occured, it would not be an extended time, nor be done over and over. If this could become reality, then the scenario changes and the real world / real life aspect will indeed point towards service upgrade.
So, if this client wishes not to spend money on service upgrade and understands all that is regarding the complete scenario, it's simply a matter of annoyance if or when the main breaker trips.
As long as the scenario does not result in barbequed bus bars or Fried Insulation / Breakers AND this does not end up bringing down the Utility owned Power Transformer, this is a design issue - and (should be) compliant to minimal NEC reqirements.
This is stepping more into the Design / Engineering areas than code compliance - with the exception of the possibility of any INCREASE OF FLOOR SPACE (like a room addition or any new out buildings, which increase the basic requirements of a service).
Being a Residential situation, this makes things a bit different as to machinery. It's for only one person to use as a "Hobbiest", and the amount of time things are used fluctuates around when the neighbors are sleeping and when the Lunch + Dinner bells ring
Now as to the future Commune of Futon Builders becoming the leasee or new owner of this location, this has no bearing towards the current "Client / Tenant's" requirements, nor do you need to design to reflect this.
When said cult of personnel occupy this location, the systems should be compliant (as per safety issues) prior to change of ownership. It is up to the new owner(s) to have the Electrical systems Engineered to meet their requirements.
In a typical "Shell" building, service size would be ample to "most tenants". Basic "per square feet" items are included, plus growth factors. Tenants with specific requirements (as to what they need for service size) require designs that include increased capacity - hence the difference between "A simple Electrical Systems Design" and "An Electrical Engineered System" becomes clear.
This message most likely is as clear as mud, so feel free to question away!!!