How the current system of trophy integration works, I don't see how this would be a good thing for the game.....it would almost immediately ruin Champion league within a couple months.
Let me explain, when you attack someone and win 10 trophies, you are actually taking THEIR 10 trophies. If everyone in the game were to attack each other in a round-robin fashion, the same 10 trophies would continuously circulate between all the players.....someone would have them, everyone else wouldn't. In order to inflate the trophies in circulation without directly involving themselves, all they did was put a '0' cap on low-level players....since you cannot go negative, when you destroy a low-level player, you gain trophies and he doesn't lose any. This small quirk in the game allowed the inflation rate to go from 3000 to about 4778 (top player) over the span of about 3 years maybe? This allows a huge and reasonable gap between leagues.
Now imagine you provide your suggestion...this is called a "money sink" (or in this case, a trophy sink) in game mechanics. For every trophy that you allow a player to pay, you literally take a trophy out of circulation....gone. Even if it is for cosmetic reasons, it is not sustainable, eventually everyone loses.
This is how it will work....high level players will not use it because they don't want to waste their hard-earned trophies, low level players will not be able to afford it as they are maintaining other important things (like staying within the 1k farming range)....so it will begin with a massive amount of mid-level players who don't care. I suspect the
1500-2200 range will be effected the most, pretty much completely wiping out the entire middle league. Without mid-level players, no one can get up to masters/champion....and hitting a champion (a lucky random draw of the "next" button) will drop them down into a pit they can't climb back out of. One by one, champions will fall down into the masters or even crystal league....a deflation at a rate much higher than you could even imagine. Eventually, if SC does nothing, there will no longer be a champion league, then no master league....no bonus loot at the top ranks at all....which means loot itself will become scarce again (because there are already money sinks in the game for that to make up for the influx from bonus and clan wars).
Economy 101....in a nutshell, it would destroy just about everything.....and all because you wanted to put some money into the ground as a fluff effect. Gold/Elixir already pays for useless stuff (like flags and statues), so there's no reason they wouldn't pay for fluff effect as well....trophies (in my opinion) are off limits for payment sake.