Supposedly there was an animation for this at some point (in one of the alphas?)
Anyhow, you can make something that is functionally similar by adding a "hold" extension to any of the tank entities. For example, if you wanted to do this with ost's panzer iv, you'd add "hold_ext" to ebps/races/german/vehicles/panzer_iv_sdkfz_161/panzer_iv_sdkfz_161_mp. Most of the values in hold_ext should have descriptions for what they do (like if you wanted to have the garrisoned units be targettable.)
You can see more examples of this by looking at the other garrisonable entities' hold extentions (halftrack_sdkfz_251_mp, mechanized_250_halftrack_mp, etc.)
I feel each one could be considered the best depending on the situation. For example, Time on Target seems like it would be ideal to use against things like howitzers and immobile anti-tank guns, since they don't move (maybe they would get destroyed? decrewed and damaged heavily at the very least.)
Personally I like the 240mm barrage best because, while it may be completely random, it sure can make your opponent mad if it drops in the right spot.
Add "-allowincompatibleReplays" to your steam launch options. (right-click company of heroes 2 in steam, click properties, then "set launch options...")
Note that if the replays are from a different patch, they may desync at some point during playback.
There was an exploit (?) awhile back that allowed commanders from different factions to be equipped in team games. This was supposed to have been fixed in a patch (late last year? idr), but I guess the patch didn't completely fix it.
When I click on the ability while garrisoned the sniper loses all vision. What I'm trying to have is either his radius vision increases or where he's aiming at.
The important is to have one of these two effects even if it's without the use of an ability.
I did some testing and it seems like the garrison sight bonus is a set value, not an addition or multiplication modifier (at least for the sniper.) By changing the sniper's sight to something low like 10, his garrison sight remained unchanged.
One workaround to your problem would be to find out what the garrison sight value is (either through the attribute editor or by comparing to other units' ranges), then change hold_sight_radius (garrison sight modifier) to match the sight increase that sight_radius_modifier gives.
For example, if the garrison sight value is 50 and you wanted it to match your ungarrisoned sight of 80 (45 default + 35 bonus) while the ability is toggled on, you would change hold_sight_radius's value to 30 (addition).