I don't quite get what you mean with the whole Mod:ing of base-pairs thing.
Right now, a point mutation call involves specifying the probability of each type of base-pair being the result. For instance, one might choose that for a particular species, a point-mutation returns 25% numbers, 50% operators, 10% commands, and 15% (insert the other thing I can't remember here).
In this way, you could specify a larger % of numbers to be returned, and you would increase the proportion of numbers in the mutation results.
Well, that's not what I meant
Another example: I created a tester bot whose DNA was a single pb, the number "345". I then set point mutation frequency to 1 and type-value slider to "100% type", put one bot to the simulation and watched. The "345" mutated to "~", then to "cond", then to "~" again. But when it got back to a number, it changed to 1. No value mutations occurred at any point.
What I think happened was that the bp was first of type "number" and value "345". When it mutated to "~", it was changed to type "bit command" and value "345 % X", where X is the amount of different bitwise commands in the program, because there is no bitwise command linked with the value 345. I can't read VB, so I have no idea how all this is actually implemented, but it seems to work this way.
Conclusion: numbers greater than about 50 are quite rare to occur in evolved DNA, because type changes will likely reduce them again.