Usually the percentage of people in tower seems to be pretty much the same for all countries, regardless of having ENY restrictions. These are some random ENY numbers I noticed last week:

About 21% Bish in tower, 26% Knights, 28% rooks

About 29% Bish in tower, 27% Knights, 25% Rooks
So if you now would kick a certain part of the AFK pilots, it would affect all countries more or less the same. So total population percentages wouldn't change much.
However, when ENY really goes through the roof (>25) that seems to change somewhat:

47% Bish in tower, 20% Knights, 16% Rooks.
But the massive number of Bish in tower is not the reason for ENY - it's the result. That's no 1h afk (dinner, work, gone fishing) people, but players that were just stopped by ENY, hoping it will drop soon (but doing nothing to help that).
Remember, it's not necessary to stay in arena to collect your 3x25 war-win perk points.
In my opinion, the long time afk pilots are sitting there for reasons different from ENY. Most of the time it will just be for reasons like securing a spot in the favourite arena (thanks arena caps!

). If you kick players after 1h, it's very unlikely to affect ENY at all.