"I'm sure that it would not take more than a few weeks for a trained software engineer to become familiar with RISC OS, and as the learning curve flattens, he would become a big contributor to the platform."
The problem is if you want to pay cheap 3rd world wages you'll get untrained software monkeys, not trained software engineers. There are good engineers in India and China, but you won't be able to get them for 50p an hour.
I think anyone taking on BASIC now would have a big task on their hands. The ARM version was written back in the late 80s, when the ARM was being developed and BASIC was based on the 6502 BBC BASIC from the Master. That code is now almost 20 years old, and I'm sure it contains some clever code in it, remember it was written when the ARM was new, and the developers were still "finding their feet" with the CPU.. Not much has been changed since - the only change I can think of is BASIC64 (to use the floating point hardware/emulator). There have certainly been no major structuaral changes, which is what people are wanting.
If you want a better BASIC, I think you'd be better writing one from scratch, maybe make it able to read standard BASIC programs and convert them to its own format if necessary. You'd need to compile the BASIC if you wanted to release it, or have a runtime library module. I'd keep a BBC BASIC like core, with structural enhancements, and a way to add in extra functionality (such as toolbox library) as additions. Something semi like Visual Basic / C#.
A new BASIC for RISC OS would be a good idea, but I don't think building it on top of the BASIC V code is the way to go.