How To Deal With Activity Steps

Dear all,

I currently have a big project seted up. It has a total of 21,000 activities.

The current level of detail of the activities is activity type per building & floor.

What I want to achieve is to introduce somehow rooms per floor & put priorities on them.

Also activity steps.

For example the activity is: Building X03 - GR Floor - Installation of Doors

And I want to end up to:

Building X03 - Gr Floor - room 1/2/3... - Installation Of Frame

Building X03 - Gr Floor - room 1/2/3... - Installation Of Door

Building X03 - Gr Floor - room 1/2/3... - Installation Of Door Hardware

For crew detailed assignment & monitoring

The room priority should be through priority column

My question is: Can I achieve that somehow without making the existing activities phases and expanding them to the above mentioned & linking them?

Thanks & Regards,

Alexandros