Puṇya is normally taken as the opposite of pāpa (yodha puññañca pāpañca, ubho saṅgamupaccagā - Dhp 412) - if you apply the meaning ‘beautiful’ to it, pāpa cannot be taken as the opposite of beautiful.
Let’s see the compounds in which it occurs - you can try substituting the meaning ‘beautiful’ or ‘ethically beautiful’ to see if they still make sense:
akatapuññena (Skt: akṛtapuṇyena) = by one who hasn’t done virtuous/meritorious deeds
appapuññā (skt. alpapuṇya) = having done little or no virtuous/meritorious deeds
apuññabhāgiyaṃ (skt. apuṇya-bhāgīya) = connected to apuñña (sin, demerit, non-virtuousness)
apuññābhisaṅkhāro = volition to commit sinful acts
apuññavantaṃ (skt. apuṇyavant) = one devoid of merit, or one having earned demerit
katapuññatā (skt. kṛtapuṇyatā) = the bhāva/nature of one who has done virtuous/meritorious deeds
mahāpuññakkhandho (skt. mahāpuṇyaskandha) = a great mass of merit
puññābhisando (skt. puṇyābhiṣyanda) = flow/stream of virtue/merit
puññābhisaṅkhāro = determination/intention to do meritorious/virtuous deeds
puññadhārā (skt. puṇyadhārā)= a shower of merit
puññakāmā (skt. puṇyakāma) = desire to gain merit
puññakammā (skt. puṇyakarman) = a virtuous/righteous/meritorious act
puññakato (skt. puṇyakṛta) = same as katapuñña
puññakiriyā (skt. puṇyakriyā) = an act of merit/virtue
puññakkhayā (skt. puṇyakṣayāt) = (due to) dimunition in the store of merit.
puññakkhettaṃ (skt. puṇyakṣetra) = field/domain of merit
puññamahī (skt. puṇyamahī) = immensity of merit/virtue
puññantarāyakaro (skt. puṇya-antarāya-kṛ-)= one that acts as an obstacle to earning/doing merit
puññapāpaphalūpagā (skt. puṇya-pāpa-phala-upaga) = one who experiences the fruits of merits and demerits.
puññapekkhāna (skt. puṇya-apekṣamāṇa) = one who seeks to gain merit
puññaphalaṃ (skt. puṇya-phala) = the fruit of meritorious/virtuous actions
puññappaṭipadā (skt. puṇya-pratipad) = the way leading to merit
puññasammatāni (skt. puṇya-sammatāni) = actions that are agreed/considered to be meritorious
puññatthāya (skt. puṇyārtham)= in order to gain merit
puññavantaṃ (skt. puṇyavant) = one who has accumulated merit
puññavipāko (skt. puṇya-vipāka) = the result of meritorious action
satapuññalakkhaṇaṃ (skt. śata-puṇya-lakṣaṇa) = having the signs of (having done) hundreds of virtuous actions
Canonical-Pali is a Buddhist register and has its own idiosyncracies - that is not in doubt. Pali (as a linguistic register) has been closely adapted to the needs and worldview of Early-Buddhism - but that doesn’t make it an entirely different language vis-a-vis Sanskrit. If that were the case, parallel early-Buddhist canons in Sanskrit and Gandhari using cognate vocabulary could not have existed. We would not be able to do word-by-word grammatical and phonetic comparisons between Pali forms and Sanskrit forms which most scholars have been doing not just in modern times but since ancient times.
The Buddha could not have been speaking in an exclusively/uniquely-EBT language like Pali to start with (O.V.Hinuber calls it an artificial language) - he would have had to speak in a language that was understood clearly by most non-Buddhists primarily. Pali dictionaries and commentaries anyways have heavily relied on sanskrit grammar and lexical sources to make sense of words and expressions. Regarding the underlying language of the Pali canon, I have spoken a bit elsewhere on this forum. If on comparison with Sanskrit grammar and lexical sources, the meanings make the sense that the Pali conveys, we’d be on much surer ground.
Those meanings of subha are not applicable usually for puñña.