As far as I know, Android is still stuck at the Java 7 language level, which doesn't support lambda expressions. Objective C uses blocks, instead of lambdas. It wouldn't be possible to just simply provide a wrapper for Java 8-style lambdas. I suspect Erel would have to build in lambda support at the B4X language level and then implement it separately for each of the three parsers. This sounds like a huge project for such a specialized function. I suspect inheritance is probably a much higher priority in B4X language development and even that's probably decades away.
However, the precursor to lambda expressions, function objects, could be hacked together by B4X programmers today with the language as it now stands. The CallSub() function gives us a lot of power.