Hi, Sharon. I have been a regular on this board for a number of years and know how most of the other regulars feel. It is simply to never paint brick. Part of this feeling is because you take a material that is basically maintenance-free and turn it into something that you have to maintain regularly. Part of this is that we have seen how many people are ready to tackle the challenge of stripping paint off brick. Once you paint it, it is very difficult to remove. A third reason is that we feel or know people who feel that they will never buy a house with any painted brick. If you do something irreversable that will drive away future buyers of your house, you have lowered the resale value of your house. This, obviously, is not a good idea.
If you are thinking of boxing in the fireplace, remember that you will be facing code issues. You have to keep flammable materials away from the outside of the firebox. One way is to use stone material and this can get expensive. Possibly a better way is to have the brick in the fireplace area removed and replaced with brick or other material that is more in keeping with your design ideas. This will be expensive and styles will change again also.
So what do you do? Your best approach is to find a good designer and tell them right off that that fireplace is not going to change but you want a design for the room that blends the present fireplace into a good modern design. If you really found a good designer they should be able to accomplish what you want.