I'm probably going to make myself unpopular in this thread but I really don't have a problem with the pacemaker. Abnett has shown an interesting way (not unique, but still interesting) way that Wally can use the speed force to overcome this problem.
There are many ways which Abnett can correct the need for the pacemaker (we know that the speed force accelerates healing and it *is* possible for a pacemaker to only be necessary until the heart corrects itself).
It also means there's more to Wally then just the Flash who escaped from the speed force and by giving him a (no doubt temporary) disability it allows Abnett to eplore more the character of Wally West to those who didn't/don't know him.
Cheers.
James.