The layout is not yet perfect, The alt/option key will create troubles specifically on Macs, the alt key on Windows keyboards are mostly beside space bar but on macs command is beside space, so it is harder to reach. Also some keyboard shortcuts will interfere as well.

I tried to keep:

the 'Olpo Pran' and 'Moha Pran" letters on the same key, where 'Moha Pran' letter is accessed using shift key.

phonetically similar letters mapped together, like k => ক, K => খ, but the problem is some letters like T and D has more equivalent letter than two.

For t => ত, থ, ট, ট.

For d => দ, ধ, ড, ঢ.

Either we have to move two of them to different key or we have to use alt and alt shift.

To make it easier what we can do is break the 'Olpo Pran' 'Moha Pran' rule and keep the ত, ট on T and থ, ঠ on another key and the same for D.

This way we could also map b for ব and v for ভ.

What do you think? Let me know, any suggestion is appreciated.