I also think adding TRC20 or Bep20 network for USDT can give convenience to their player and possible prospects. Like for example, I also use USDT but I seldom use Ethereum network because of too high fees. Often times my USDT is in Trc20 since we can move our fund with cheaper transaction when it is done in TRC20. BEP20 too is a good option to add since BEP20 had lots of project bult on its ecosystem and there are also lots of supporter.
This is just a matter of time if indeed the demand for alternative networks is quite high then Duelbits will do it for now the ERC-20 and BEP-20 are enough
TRC-20 may be in the next plan if the Tron Community asks for it including you, can send an email to the support team as a suggestion,
If there are 100 same suggestions every week then I'm sure they will do it.
If the community demands then surely they can think of adding another one but they also have to consider lot of factors while making such decisions and coins should be popular and demand also.But I think at this time also the deposit options are good but if there's demand they can surely think about it.