Yes, indeed I agree with you on your point of those exposed bolt heads, since this rear set intends for its use with the original signal lights in which those bolt heads are covered by rubber parts. On the other hand, I like those Lucas-style signal lights instead of the original ones. I guess that something should be given up to get something.
Thank you for your suggestion! I have just started to think about any possible ways to improve the looks, perhaps using the caps to replace the original rubber parts as you suggested. I will let you know if I could come up with any solution.