You could put in anything pin-compatible. But this doesn´t make sense as long as you don´t specify what you want to improve. Different opamps have different parameters which are optimized for different uses. There´s no such "better" opamp like many half-educated gearslutz will tell you. If a circuit is designed well then many weak parameters of an opamp can be designed out of the way so they will have no influence at all on the circuit.
Deltas have very very well designed circuits e.g. many unconventional solutions are inside to improve performance. I have highest respect for the designer´s (Douglas Self and/or Gareth Connor) work. Simply exchanging chips will not attack at the weak point. You´d better think about recapping and increasing coupling caps in strategically important places, maybe adding bypass caps and buffering the rails locally at the chips (if space allows). This will improve your desk´s phase margin and transient response so much more than thoughtlessly putting in some überchips.
New chips may need circuit tweaks to make them work stable. Are you able to calculate this? Are you able to measure instability? Probably not, otherwise you would not ask here but simply do it (no offense). Ignoring this fact may turn your desk into a ham radiostation.
New chips may have or certainly will - in case of replacing TL072s - have a higher power consumption. This will increase PSU load and may create thermal problems. Is you PSU beefy enough to supply the needed current?
There are many threads here about this subject and many members have refitted TL072s after having tried modern superchips for one reason: TL072s do have a sound of their own which seems to work very well in the mix, esp. in EQ-circuits.
The monitor section is another can of worms, though.
