I only see down air as a safe option on shield at the moment and honestly, it’s just not very fun to use. Kirby’s down air from Ultimate is a little more satisftying to use as you can combo it into a quite a few things (If Gouie’s downair actually combos into anything then please let me know because I haven’t figured out a good use for it yet). Of course, this move would have to be adjusted a little bit like making the spike not as strong, but I think it would be cool for Gouie to have.

Gouie’s dair can combo but only at high percent