May I focus back to the original question, "necessary to base bevel" !
The answer in my opinion is not a clear yes or no .
It depends on; the ski, the skier and the ski conditions you will be on most of the time. Of course the skiing context will also determine the correct answer.
If you read carefully most posts on ski tuning and watch most tuning videos ( many experts ),,,,you will note that ski tuning practices are derived from racing tuning procedures. The goal is to go faster. To set an edge on hard icy slopes.
Not so on powder skis.
So,,,, so on "transitory" powder skis ( +100 to 110 mm ) .
You have to determine where you will ski most of the time.
I have several skis and tune them differently.
I never bevel my powder skis.
I always bevel my world cup racing skis.
One rule of thumb that is vital is , you must have a flat, clean base. So get a true bar above all.
The rest,,,,is up to you.
I hope this helps.