I don't have an issue with the original lights providing people indicate well in advance of applying their brakes which, IMHO, is how they should be used.
However, even if they don't, the vehicle following is still going to get the brake light, even if the indicator is wiped out by it, they might wonder what the hell they are doing but the main information that they are slowing down, for whatever reason, is there, and that is the most important information the following vehicle needs.
Yes, those that have the Weiser, or similar, devices fitted can be clearer, but the first time I saw one in action I did wonder what was happening when I saw one multifunction light glowing red, and the other flashing orange. Then there are those that fit additional brake lights that light up the back end, distracting from the indicator, so not a massive improvement on the OEM set-up.
I believe that there is a set-up where you can turn the multifunction light into just indicators and fit the additional brake light above or below the number plate. If I was going to fit anything, this arrangement would be it.
However, I'd check my insurers were happy with the modification as you are now changing how the bike works which has an affect on the certification of the bike. In the event of an accident they could refuse cover if the mod isn't declared and accepted.