It is tricky…
There are 2 valid arguments.
Historical accuracy.
Aircraft like the Italian F-16 were acquired for the sole purpose of giving Italy a AMRAAM equipped fighter as a stop gap to the Typhoon as they did not want to invest in the Tornado ADV like Britain did. So they leased F-16s instead. Same with Sweden and the Viggen D. It’s entire purpose was to intergrate AMRAAM onto the Viggen airframe. On these grounds, these aircraft could and perhaps should get the weapons it actually had IRL
but then there is the game perspective and what Cpt_Bel_V is getting at.
BR Placement
Are these aircraft needed at the increased BR or will they even be any good. In the case of the Viggen, probably not and probably not worth the BR increase. Maybe a second airframe and give people the choice, but its unlikely it would be an effective platform and few would play it.
In the case of the F-16, it could be fine, though the limited CMs are certainly something to pay attention to. But it does create a Gap, though one mitigated by the presssence of Hungary. But without the F-16 at 13.0, you would basically jump from BVR trucks like the Tornado and Harrier and straight into fightrers like the F-16 and Gripen with nothing to really bridge the gap except for the Mig-29.
At the moment, that isnt really felt much, because the F-16 is so close to other ARH slingers, but in a year or so, when 14.3s enter the fray, you may be thankful to have an F-16 at a BR where it cant see them.
TLDR: There are 2 valid arguments that are directly polar opposites to each other. What is really needed is a solution outside of just adding and then moving. Like a variable BR, where everyone is happy.
Enable Advance weapons. F-16A ADF moves from 13.0 to 13.7 and has access to Aim-9Li and AMRAAM.
Disable Advance weapons. F-16A ADF moves back to 13.0 and is limited to Aim-9Ls and Aim-7Ms.
No gap created, no additional grinding needed with second airframes, everyone can play what they want, when they want and where they want it. Easy.