Hi Luis,
There are NO guarantees and the risk to do the swap MUST BE entirely YOURS, but here are my thoughts on the matter...
It should be no problem as long as the mechanical and ELECTRONIC specs of the 70W tube are the same as the 60W.
Are they from the same manufacturer?
Are they both RF driven?
What RF voltage?
What drive current?
Is the tube diameter for mounting the same?
Is the beam height when mounted the same?
The optics for the 60W will work fine with the 70W as they are not dependent on power just raw beam diameter and the 60W and 70W will probably be pretty close to the same at around 1/4" diameter.
The power supply for the 60W **may not** generate enough current to drive the 70W to full power but I would be surprised if that is the case.
If the power supply does drive the 70W to full power then the software however will still adjust power from 0 to 100% meaning that at 50% with the 60W you would have 30W and with the 70W you will be getting 35W for a 50% setting. Experimentation will decide where you will need to adjust the burn power for the 70W.
As I said at the start, these are my thoughts and I MAY BE COMPLETELY WRONG. So make sure you have everything well understood before doing the swap. If you do not FULLY understand what you are doing then hire someone who does.
Given the cost of a 70W laser tube, a faulty assumption on your part could be costly. There are many many variables in driving a laser tube, it is NOT like changing a light bulb.
Dave