I’m not exactly sure about how the layout/arrangement described by you above would actually look like, so I can’t give you much of an answer there… however, the bomb tower boost doesn’t increase their damage output, so if you can create a situation where with an unboosted bomb tower you can fire way ahead without being in range of attacking troops, then it should be worth doing it, as it should be as effective as a boosted tower, damage-wise. The question is mainly, can the bomb tower really reach forward far enough without being in range of cannons, without its boost, in the situation you describe?
Anyway, putting in my two cents of knowledge, you might know about how you can place firebolt towers in a way they can fire ahead (onto a tile where it is diagonally adjacent), while it is actually facing another tile (way further into the base) that it is straightly adjacent to, then being out of range for anything except cannons, while still being to fire onto the earlier tile? The same thing can be done with unboosted bomb towers, and those are then even unreachable for cannons. However, their coverage of the earlier path tile is then very limited, so whether or not that is an efficient way of placing them is another question.