Brother :salam2:
We should not try to mould Islam according to own impaired understanding but should appreciate what Allah has created and what we use naturally to make our life easy. We should know that all languages are creation of Allah and that Allah has created these languages to make human communicate with each other. Similarly, all symbols (scripts) to write particular sound is also creation of Allah, who created them so that humans can write the sounds of what they communicate.
Further, there is no language of Allah as Allah is not dependent on any language. Allah has used Arabic to send message to Prophet (SAW) because language Prophet (SAW) used to use was Arabic. If Prophet (SAW) was sent in China and was using Chinese as his language then we would have had Quran in Chinese. Further, Quran came in sound not in written form, and it is people of that time who used symbols they knew (Arabic script) to write that sound in written form.
Anyhow, coming to your post:
Well, writing ‘Bismillah (Roman script)’ is symbol of a sound that only those can make when seeing this symbol who knows Roman script. Those who do not know Roman script, for them this word ‘Bismillah (Roman script)’ is meaningless symbol. Still, you wrote ‘Bismillah’ in Roman script and expected that I plus all on the forum would be able to read it properly as ‘Bismillah’ written in Arabic script. … So, how come you used that symbol Bismillah (Roman script) in your above post and expected that all on this forum would read that same as Bismillah written in Arabic script?
Well i couldn’t find in any hadeeth neither in Qur’an where it is mentioned that 'Bismillah (Roman Script) is perfectly fine to write neither i found that 'Bismillah (Roman Script) sounds Bismillah (Arabic Script). Keep in your mind these symbols never used by our Prophet Muhammad 
. Moroever its not mentioned in Qur’an also (as per my knowledge). neither by any companions nor by our four Imams
Why symbols we learn to use in uni is something different than one Muslim learned (using 786 as Bismillah-ur-Rahman-ur-Raheem) much before they even knew single letter of Roman script … or scripts they learn today in University?
As for your saying that we should write Bismillah using symbol of any script but should not use symbol‘786’ to write ‘Bismillah-ur-Rahman-ur-Raham’ … so why?
What is big difference between a symbol ‘786’ to produce sound ‘Bismillah-ur-Rahman-ur-Raham’ or use Roman, Arabic or any other script to produce sound ‘Bismillah-ur-Rahman-ur-Raham’?
Can you please show us any Quranic ayah or hadith that says that one can use Roman, Chinese, etc … or any script that is taught in university to write ‘Bismillah-ur-Rahman-ur-Raham’ but should not use ‘786’ to write ‘Bismillah-ur-Rahman-ur-Raham’ … a symbol that Muslim knows and learned much before they learned these scripts (Roman, Chinese, etc)?
Can you please show any hadith or Quranic verse that says what you mentioned above?
Anyhow, as for me and to most who know/recognise ‘786’ as ‘Bismillah-ur-Rahman-ur-Raham’, when they see symbol ‘786’ and read ‘786’ they produce same sound when they read ‘Bismillah-ur-Rahman-ur-Raham (Arabic script)’, and thus it is perfectly fine to write ‘786’ when intending to write ‘Bismillah-ur-Rahman-ur-Rahim’.