They are literally designed to be upgraded. Paras get slightly better guns and 1 more man than rifles but cost significantly more and come at CP3. At that point your vetted Rifles would be stronger to significantly if they have Bars so the only point in buying them is to upgrade them.
Yes, but again at 2 CP mark you have your established army more or less, you have muni to upgrade them instanly or not. Its wrong to compare them to the starting unit when you are not only dont have a lot of units to support them, but also you dont have muni to spare.
Also having literal penal damage is still good, because penals damage vise are very strong squad, especially considering that at 2CP mark there are not so many vetted\upgraded squads running around.
Your are vastly exaggerating how weak PF are to start the game, both Isildur and Kimbo used a 2VG/2PF opening against USF and both won decisively. They did it in the AECOH tournament, which leads me to believe that these ELITE players thought that the "weak" start was worth it for later gains.
EDIT: Rewatching, they both also upgraded their PF squad first my guess being other than DPS the extra 7 sight helps immensely when screening for the FlakTrack.
Well they are elite players for this reason. Good players can only play with soviet T1 oppeninings against osts and not fall badly behind in map countrol. In their games its more about outplaying your opponent by possitioning\taking engagements not about units themself. They are not really a reference point imo, since you know OKW in 1v1 is a trash faction judging by the stats, while good players can present it like its a cake walk.
Point is, PF are frustrating to deal with, but imo its because their DPS is concentrated around G43. If their power was redistributed making their regular rifles not suck balls (and be better in early game in return) while tonning down G43 upgrade, they would have been fine. Since at least they would have suffer from model drops much more significantly.