One can argue endlessly and seek the support of the scriptures for his own deductions.
DronAcharyA was not a born kshatriya as per the narration in mahABhArathA. His father BhAradwAjA (by most accounts a Brahmin) went to the river Ganga to do ablutions and being unable to control his desire at the sight of GritAchi, an apsara, discharged reproductive fluid which was caught by him in a pot/vessel which was known as "DronA" at those times.
If a non-kshatriyA, DrOnachAryA could be a warrior of par excellence capable of vanquishing 60,000 kshatriyAs single-handedly there is no reason why a sUta-putrA could not do so.
Of course this aspect of DronA being a non-kshatriyA would be dismissed out of hand as a case of "exception " and the incidence of "karNA" would be touted as the case that proves the rule.
But if one were to even jockingly allude that DrOnAchAryA was the first case of a test tube baby the scientists in this forum would jump up demanding proofs.
Yes. There are many other angles too.
sUta-putra or not, Karna did become the King of Anga Desa. He fought the Mahabharatha war as the king and ruler of that province. If Karna remained a Shudra despite his warrior capabilities and if Karna's case is taken as a rule, then it could be argued that there is no restriction in a Shudra becoming a King; so the varna system at the time of Mahabharatha was not exploitative.
IMO, the Mahabharatha war is about retaining the kshatriya status of the Pandavas. Pandavas when they returned from exile wanted their share of empire to which Duryodana refuses. Krishna says there will be great destruction in case of war and asks Duryodhana to give Pandavas at the least five villages, one for each brother. Why? Because each brother needs to be a ruler of at least a village to retain their kshatriya status. If birth alone was enough to guarantee their kshatriya status, there would have been no need for war. The position that jAti determined by birth and occupation determines varna seems to be the correct one. Of course, when jAtis determined by birth are classified/ordered in the varna system, it gives a mirage that varna is determined by birth.