M410iC and M410iHw Base Compatibility

Wouldn't that give you a lot more work though?

If you're referring to the 4 legged base where you have the controller underneath, you'd have to take out the controller cables, pull the robot out of its base with a crane and then reinsert it into the old base.
I think it would be a lot more work than simply replacing the whole arm with the new one.

I would fab up a new base, I have seen the old bases begin to start cracking at around 100,000 hours.

Not to mention all of the addional work as mentioned by ClaudiuA

Quote from M_Benton

The thing is, we don't have a base for the M410iC, and since they don't want to use the M410iHw anymore, we wanted to maybe save some money by using the same base installed. I don't know if this is recommended at all.

I am actually pretty sure this will be quite costly for you, unless you have some heavy machinery available.
I've never actually pulled an M410 off its base, though I do have to do it soon due to some grease leakage from under some of these guys.

Well, pulling the robot off its base should look something like the image - this is the 410iB. I don't have any manuals for a MW robot, soooo...

Quote from M_Benton

We have removed a robot from it's base once, so we do have the machinery available.

But now that I am looking at the M410iHw, it has a motor just underneath the base (check attachments), so I guess their bases must not be compatible?

Well, since one is a twenty year old weldment, and the other is cast, I would say no.