Arrowstar, stumbled onto the work and threads and I have to say great job. Some for-fun suggestions for add-ons that might be of interest if you continue developing the tool:
A low-thrust transfer addon using exponential sinusoid trajectories:
Dario Izzo (2006) Lambert's problem for exponential sinusoids. In Journal of Guidance, Control, and Dynamics.
http://www.esa.int/gsp/ACT/doc/MAD/pub/ACT-TNT-MAD-LMSP01.pdf
-This can easily be modified into an alternative Lambert solver and makes for some fun trade studies (bigger launch windows, more solutions, etc.)
Addition of a differential evolution solver for the optimizations (shown to work quite well for this problem):
Given a range of dates, flyby sequences, etc, a relatively straightforward approach with nice straightforward open-source solvers in multiple languages - including MATLAB
http://www.icsi.berkeley.edu/~storn/code.html. These will help produce globally optimal solutions rather than locally optimal ones, and is especially helpful for multi-flyby solutions when the Pork-Chop plots can no longer be used.
Implementation of the Gooding algorithm for the Lambert solver (known to be one of the most robust approaches available, converges when others method such as p-iteration have trouble)
R.H. Gooding, "A procedure for the solution of Lambert's orbital boundary-value problem
", Celestial Mechanics and Dynamical Astronomy
Volume 48, Number 2, 145-165, DOI: 10.1007/BF00049511
A Kepler Solver to visualize the trajectories in position space:
Using F and G series as taught in astrodynamics courses at Purdue. This way you can see what the trajectory looks like. (You may have already done this).
Keep up the great work.