Adding full sleeves to a strapless dress

I bought my dress in November and I’m going in for a fitting in a couple of weeks. The shop can do any alterations as they design all of the dresses. Caught up in the magical moment I went for a strapless dress and ordered off the shoulder sleeves to add on. On further thought I think I want a bit more coverage on the top half and have full length lace sleeves. I’m just worried it might look obvious they’ve been added on. Has anyone else added full sleeves to a bandeau dress and willing to share the pictures?