Problem of colored-coins/assets and other coins with a parent/child relationship of paying for fees with only the parent currency
It's definitely a common problem found in a lot of those platforms that make it easy to create your own colored coin/token. Asking users to acquire the native token, such as Bitcoin with Counterparty and NXT with the Nxt blockchain, is usually not a good way to start off your relationship with that customer. Some people may be fine with it, but it greatly hinders mainstream use. 

Ardor solves this problem with child chains that allow child chain creators to have the users on their child chain pay transaction fees in the child chain token. A bundler (could be the child chain creator) would collect these fees and pay the Ardor main chain for transaction processing. So, ARDR tokens would still be needed, but your users wouldn't need to touch it at all. 

You would still need to re-distribute your acquired child chain tokens though, but the Asset Exchange that will be on Ardor will be a great way for you to sell them back to your users. If a USD child chain exists (kinda like Tether and USDT), then they could purchase those child chain tokens directly with those USD tokens, much like getting game tokens at the old arcade.