PLEASE HALLLP. Dilemma for batten board

My husband and I are doing BB for our entry way. But we have this random upper part of stair case stringer. Ideally I’d like to go higher than that but feel like it just randomly chilling in the corner would throw off the whole look. Then my husband said why don’t we use the upper piece of the staircase stringer and follow that all the way across as our upper most piece, but I think that will cut the room in half too much and wanted to go taller.

Any advice - entryway is still a huge work in progress but wanted a picture to show was I was talking about

Please help