It's not something you can really force. I am not a fan of (trying to) replace the existing Paste buttons in a program. If the program crashes, all the rewrites are still in affect...
But I did recently have a client with the issue. While in the end they decided not to release the change, what I had done was use a Change event to apply a Style to the cell. If there might be formulas involved, you can also add a paste values to that. But - at the same time, this was for a specific part of the sheet and one sheet only. It's not something I would apply to all sheets and all cells as it can slow the workbook down.
If the users are disciplined enough, you can add a custom Paste to the right-click context menu "msklut's Paste As Text" and even assign it to a custom keyboard combination. Though.. not 100% sure if accessing a Mac's context menu would be the same code as PC.. Mac's are fussy that way.