Would it be offensive to a chess coach to hire another titled player just to play training games with? Say I have a chess coach, but I hire another titled player to play training games with. Would it be offensive or alright to do? Or they would they care as long as I'm paying them?
You are the customer, therefore you can spend your time and money as you see fit.

From your coaches' point of view, they would prefer it if you didn't use the services of another player. After all, any professional who is paid on an hourly basis would prefer to have a monopoly on a revenue stream and work 100% of the hours that you are paying for. But that is your coaches' problem, not yours.