We have a garden full.... After several years we still have some good ones.. As you said, the majority are nasty but you get the occasional one the does work well.... The garden is now full of mismatched solar lights.... In the dark, who cares that they are dissimilar...
I was planning to make little stainless steel frames and put all the good ones together... The little square solar cell is normally the same size... The AA batteries are also the same, so it's not unreasonable....
I feel that they are NEVER waterproof, and that's what lets them down...