Just don't do this. Sure, you perform a tilt, but it's a slower. Practice doing it the hard way because it pays off. It won't take you but a week and you'll be doing it fine without the delayed pressing of A. You'll be faster and better off.
Also, doing the pause then A thing won't work with tap jump on. You'll just jump and never have the chance to do the up tilt. You can disable tap jump and do it, but then you can't UpB out of shield. Even if you don't do that now, you probably will and you'll have to relearn how to do tilts. Also, if you learn how to do it this way you won't need to buffer. As far as I know, buffering tilts (try jumping, holding down on the left stick and then hitting A when you land while still holding the down direction) isn't any faster than just performing a tilt; it's just easier.
TLDR; learn to do tilts correctly and it will help in the future.