KMS would you be so kind and describe, which problems you have with current PLCs, because I can't follow any more.
You started with the requirement of a loop, a slow down or pause possibility, if I'm right. We explained to you, why this isn't a good idea on PLCs. Now you came up with the claim, that math functions are nearly not existing in LAD and FBD, which is, in my opinion, not quite right. There are many mathematical functions in different libraries and they could also be used in LAD and FBD, the question is, if it is really wise to do so and I would say no. LAD and FBD should be used, in my view, for logical things and for the more complex problems SCL/ST should be used.
By the way, there are PLCs with which you can use other languages, for example with Beckhoff TwinCAT you can use C++ and also integrate MATLAB projects.