So, limitation to non-plus models seems to be nothing more that your wish. Sorry!
... regarding the Plus version, which BTW only confuses SSAX newbies,
Just and only this what you said - due to reasons.
In worst case some peoples may bric they new instrument due to mess.
I did not mean this just to @Kibabalu but he was just now randomly in front. Overall I wish we try make this bit less messy. 2016, 2017 it was simple due to fact there was only SSA3021X and 3032X.
Now we have SSA3021X and 3032X and then we have different new hardware machines SSA3015XPlus, 3021XPlus, 3032XPlus, 3075XPlus. Then we have VNA's SVA1015X, SVA1032X and SVA1075X and after then real time spectrum analyzers SSA3032X-R 3050X-R and 3075X-R. And perhaps more is coming. Some of these product lines need handle separately for avoid total mess. And more is coming so my opinion is that least around this time now we need organize and arrange these so that they all are not just big messy mix. Later it is more difficult, even now it is difficult.
Specially if we talk about experimental HW/FW changes where always is easy road to make mistake what leads to failures. And much more easy when some newbie is totally messed when all information is here and there and everywhere in nice messy mix with sugar and pepper. Of course we who have been here before beginning can quite easy follow what is what but my concern is newbies or other peoples who do not have so much experience.
I hope no one goes to troubles and permanently or less permanently find themselves with bricked SA.