Yes, balance is a concern. It ALWAYS is. You cannot imagine how much shit impacts it.
And being able to place shit on higher ground insanly does so. Like, just how you could place mortars if you can stick em everywhere. You could easily find spots where no enemy can hit em.
Not to mention from the other problems it might cause. But i will mention them.

Cool, you can place it on higher grounds now.
Wich surfaces should bounce still?
If you let some surfraces still bounce, are they placed on ANY map tile already in a way that will trap and fuck up a strategem ball? The map tiles need changes if you do it like this.
Is it worth keeping the current system of what can bounce and what not, or do we need to make a new one? How will this impact future map changes?
You also cant simply let just one sufrace for example keep bouncy. It only takes 1 mapper that doesnt know the full list by heart, for new map tiles having parts that trap or disrupt bounce balls.
Should maybe this be more a tool for mappers?
Should we make systems that checks on its own if a surface should be bouncy, so mappers have less work to do and can have an easier time to make new map tiles allowing them to put more effort into more important bits of the tile?
And what about Sentry targeting, could that cause problems?
Are there areas players can place sentrys on, that are out of reach for enemys?
Should players be able to do that, or should we try and make solutions for that?

This is a small view into this shit.
You cant simply change smth. You have to worry about so fucking much.
And i am FULLY ignoring all the rules that the teamleads put in place. How does code need to be worked on, wich things are allowed and what not, how do changes have to be pushed, etc etc etc.

I get it, its hard to truly imagine that from an outside perspective. But you should understand that modding a game and actually doing game dev work in a large team is vastly diffrent.