I can help you with this but before I do I need to make a declaration. I'm in trouble with the moderators for being forthright in my replies. For me, the power of the help forums is in the quality and accuracy of the responses, I never reply to a thread if I haven't got direct experience of the topic. If it is just my view rather than factual I will make that clear.
IMHO, information given, which may be given in good faith but inaccurate or unrealistic is about as useful as a chocolate teapot.
Therefore, what follows is not meant to demean anyone, diss anyone or insult anyone.
Right, that said, removing these bolts is tricky. The head thickness and therefore the depth of the hex hole is shallow - there is a picture below showing the BRP bolt next to a standard hex bolt, note the head depth.
Because the head depth is shallow and because the bolts are very effectively glued in place there will be some bruising of the hex due to the force necessary to turn the bolt, consequently your technique needs to be very good.
You rightly say the BRP hex is 7mm - no other size will do.
The hex tool needs to be good quality.
You MUST keep the hex tool end absolutely inline with the centreline of the bolt.
I have removed these bolts using a hex key and also removed them using a hex socket and breaker bar. The breaker bar on an extension is the better option because it gives good clearance of the bars but a hex key with an extension is perfectly possible.
Do not apply heat, it is futile because the aluminium bars will conduct the heat away from the bolt head and also you risk damaging the plastic powder coat on the handle bars.
There is no special requirement other than to ensure PERFECT centre alignment of the tool and the bolt at all times, any squintness of the hex tool will cause the hex to wind out sideways and wreck the hex hole.
My recommendation to you for replacing the standard bolt is not to use a locking compound on the thread but to use a dab of grease, I'm not going to go into the reasoning for this but it's based on experience.
Since I don't know you, be sure you have the skill before you start.
There you have it; dry, to the point and factual. I'm not here to be loved but I am here to help. Take care and good luck with it.
Edit: I see the post above has come along and posted while I'm typing this. It recommends heat and impact. There is no intention for me to diss those comments, it's simply a different view posted while I'm typing.