But all these changes will increase weight and rise costs...
With extra weight you are getting alot of extra thrust that will more than ofset this.
Putting in F-119 would further increase costs due to required redesign. Doesn't makes much sense.
There would be some cost in redesign. However you dont just throw away a capability because of some extra cost. The whole point of this more capable F15 is to ba able to defeat more capable advanced flanker variants that will be able to supercruise with the AL41F which is in the pipes. So unles you put a version of the F119 the major threat aircraft will have a large kinematic advantage. And the production lines on the F119 are open now, so i'm not sure the cost would ofset the capability.
A TVC equiped derivate of the F110-GE-132 would be a cheaper and still good option IMHO. You also don't need canards if you have TVC.
A F110 will still be a F110 even with TVC and will be compleatly outperformed by the AL41F. So then the whole pint of this upgrade, to have a more capable platform that advanced flanker variants, would not be met.
And canrads are very usefull even with TVC. F15 MDST, F15 ACTIVE and SU30/37 all have both for a reason. TVC helps your roll rate, sub and supersonic manuver, however a combinationof TVC and Canards allows a platform to generate massive angles of attack which is vital for WVR combat, which TVC alone will not come close to matching. And therefore if you leave them off you hand the primary threat platform an advantage.
AESA equiped and networked F15's allready has the avionics, SA and networking advantage, with these upgrades which have all already been designed and tested, the only advantages the flanker has (which are big), its raw performance will be in the F15's court. But still for the USAF, the money would be better spent more raptors, which would still be much more capable.