There are plenty of journals using ScholarOne. The problem is that your site does not have a single login or allows for the merging of accounts. In my case, this concerned Proceeding of the Royal Society, EPL and some other journals.
You create a single ScholarOne account, where I can put in all my information (affiliation etc.), I provide a list of my email addresses and can link it Orcid. Or at least give the option to merge accounts to have a single login.
If a journal wants to invite me as referee based on my email address, they just type this email address in your system, it recognizes that my account exists and when I login (plus notification email if I approve this) I can see the request and approve/decline.
This way I don't need to have logins for different journals and retype the information every time a journal wants me to referee a paper in your system
When I login on your main page, it should show a list of all the journals, which I have already used.
Most other journals/services using a shared website allow joining of accounts.
Of course, I'm aware that you are only able to take suggestions, but I know quite a few colleagues who stopped refereeing for ScholarOne/ManuscriptCentral because it's just chaotic and one needs to deal with so many different logins if enough journals approach you...