slightly pushed in softdome tweeter on Fritz speaker

^Nice suggestion...or anything that will be gentle.

Rather than regular Scotch tape, try blue painter's tape or masking tape. It's a bit gentler on surfaces.

The dent will unlikely cause much of an issue regardless.

I've successfully used a vacuum nozzle.... carefully.  Guide the nozzle keeping it away from the tweeter so as not to create a damaging suction.  Some vacuums allow selection of weaker suction power.  It''s like fielding a pop-up fly, use BOTH hands.

Might sound weird, but how about a turkey baster? Just pop the squeeze bulb off the end and gently place that end over the dome while sucking on the small end. Same as the vacuum cleaner suggestion but a whole lot gentler and easier to control. 

This is exactly why I made slide-over speaker boxes from black matboard material for my Sonus Faber Sonetto V G2. I just slide them up and off to play and slide back over when done listening. They have saved the day from sweepers or knees, etc in tight entry way.