So what were you going to fill the hole again, and then drill a hole for the cables?
Bricks are not taken out to run cables, drill a 1"dia hole then 'fish' the wire through. just needs a little thought.
Don't fit wireless, just think of all that battery changing.
How do you think all alarm systems were fitted before the good old wireless came along and everyone then wanted no cables showing.
No cables showing, do you honestly think that it was not possible to do that from the start of the alarm industry, well it was if really required.
In the past I have run cables down cavities between many floors both in houses and offices. It takes a bit of fiddling but it's not impossible.
Get a cable into the airing cupboard and from there into the loft and then drill into the loft from outside and then run a long length of fencing or coathanger wire into the loft as a draw wire for the cable.
You said,
.......................................... looking for the most reliable
For once Bernard is completely right.
Did I actually write that?
That might make it a little easier for you.