ding ding xin xin
wei wei chou chou decade-yi wei
Indeed, JR, in Mangpai Bazi, we don't use the follow type charts. If your chart was follow, then LP Yi Wei would not be reasonable as you said.
LP Wei:
1) Wei has the same image as Ding, so it's the occurrence for Ding to control Xin. Of course there is a limitation from the natal chart, Xin cannot be controlled well, because Xin is too strong.
2) Wei is naturally the "arrival" of Wei themselves (your Day and Hour Branches). So it's also the occurrence for Wei to control Chou. Of course there is a limitation from the natal chart, Chou cannot be controlled well, because Chou is very strong.
So it's a reasonable LP all right, but not great.
LP Bing Shen: Bing has a drawback, because Bing combines with Xin. The intention of the natal chart is to control Xin, so combination is against the intention of the natal chart. This is how Mangpai works, the luck pillars had better follow the original intention of the natal chart.