I quite like the plan for this build moody, should look pretty cool! For the lighter centre, is there a lighter stain you can get your hands on? Also the burst will darken as you apply more stain to it, allows you to further build up on that blend. I wouldn't go for the blue, won't match the body stain unless you are looking for that specific finish? I'd definitely try it on scrap wood. Possibly get some wood and apply your burst to it, then prepare some of your mixed varnish and apply to one half only, then the other half with straight varnish, I've done that myself in my woodworking classes to see how certain finishes turn out and gives you a straight side-by-side comparison!