Inside 100 diameters is a 5-point penalty, so if the rules was a one-point penalty per parsec of jump, and a one-point bonus per level of Jump program, at high TLs low-diameter jumps become reliable if they're of short range (and your computer has sufficient power).So maybe this is why there's the 100-diameter limit, outside which these n-bodies reduce to negligibility and allow much simpler calculation. It's jumping inside the limit where you definitely need to juggle n-body math, which apparently they still can't do at TL15.
It might be interesting if very high TL computers could jump closer than 100 diameters.
Add some variability to the sub-100 diameter penalty for more variety if desired - say one point per 10 diameters under down to 10 diameters, and a further -1 per diameter under that. Then allow a Jump-7 program, so those with really big computers have something to use that capacity for.