You're right, 1/3/4 is one family, while 2/12/16 is another. Also, it's, at least as of now, useless to have tags for every model. So maybe two tags (plus CoCo) will do it.
There is one caveat about the writing, as the Model 1 was writen using an arabic numeral, *notnot a roman. Only later on (*1) Model II and II used roman designators, while Model 4 and everything thereafter used again arabic ones. So for our purpose of a clear reading, esecially since tags are lower case, using roman numbersarabic numbers for all would be apropriate.
Having a generic Tandy tag might be a good idea as well, so questions can be taged tandy + trs-80 model 1 family allowing a more generig selection and a specific - as well as using tanyalone for more exotic Tandy hardware.
*1 - One may guess it was inspired by the Apple II where the same switch from arabic to roman was done before