Interesting one.
Are you reasonably remunerated on the CL30? If so hopefully that will continue!
If the owner is typing you etc I wouldn't be looking for the sort of rates people are quoting here for freelancers. If he bonds you get the experience then you can enter the market with time and name your price. It's an expensive type.
Ready to be yelled at but.....
In a way I do feel slightly sorry for an owner upgrading. They have everything set up, pilots hopefully on a decent package and everyone happy. Said owner then upgrades, spending a lot of dough on a cracking machine but essentially still a jet, albeit one that does 4000nm more. Then suddenly he is expected to pay the same guys doing the same job with longer sectors 30-40% more. Plus the training costs.
But I won't feel too sorry for them!