Definitely, but PRISM should never send BTNs with invalid dimensions to the InSim host. It should keep a list of buttons with all their parameters and always send the complete BTN, the packet size remains the same so it really doesn't matter.
The added advantage is that PRISM can determine if it's actually necessary to send a button at all, which is particularly useful with high frequency triggers like MCI/CompCar at 50ms/20Hz. For example, if the application is to send the yaw angle as integer, it's likely to remain identical for several packets in succession, so sending the button again would be a complete waste of bandwidth and CPU cycles.
A sendButton() function/method would therefore check the provided BTN against the list of stored BTNs, compare BStyle, dimensions and Text and only send the new BTN if something's changed. It could also allow for a simple text update, like sendButton(ClickID, newText);