[ArKay99]

You can do this in Studio One. I used to stop the transport in Pro Tools because of this. In S1 I can add tracks (either audio or Instrument tracks), add FX even to outboard, even UAD stuff. I can remove tracks, change assignments, etc. I used to cringe when I found out you can do this and started doing it. Now I try stuff to see if I can make it hiccup. The only time there is the slightest issue, and it doesn't cause any transport hiccup is if I add a UAD plug while there is audio playing on the track. Depending on the 'weight' of the plug and I guess how much the DAW is contending with I'll get a pop or click. It's really cool. You can even set it to 'record to layers', so that your stuff is recorded to a new 'layer at the beginning of each loop. Then later you can 'comp' (edit pieces of) the good layers together into a killer track

For tracking this way, yes Pro Tools is a dinosaur, but for mixing it has a lot of great stuff that I miss. VCA style groups is one off the top of my head. But S1 is only at version 3.