Is updating custom field data with +/- similar to tags possible?

Hi all,

I’d like to be able to track some fine-grained info about a user as custom fields. I’ve tried multiple ways of getting something acceptable but can’t seem to find a good solution. Firstly, I’d like to be able to have a Number custom fields and update it with “+6” and “-10” values, but instead it only can be updated and not added/subtracted from the existing value. Similarly with a multiselect, I’d like to able to add items to the set like in a field like PagesViewed {page1: true, page2: true, page3: false} by sending mt(…, {pagesviewed: {page3: true}} and have this update page3 to true without setting page1 and page2 to false… I know that I can sorta use tags to get something close to this, but I’d really like to be able to be able update custom fields on the contact so i don’t have a giant collection of 100 tags that really should be broken up into categories… I also don’t want to have a separate custom field for each of these. Are there any other options? If I could read a contacts data via their mtc_id that would also be very helpful…

Not possible right now.