The DTR system really isn’t geared up for repeaters. It’s frequency hopping - picking the clear ones dynamically as required. This means that the fundamental operation of a repeater is compromised. They must have sharp filters that stop the output making the input desensitise. You can get smallish cavities that work fine with an 8Mhz split in frequencies, and you can get even sharper and more expensive cavities that can do less than a Megahertz split. With the Motorola system as far as I can see there’s no way to make the things NOT frequency hop. The analogue idea of linking two radios would still work, but as soon as one fired up, the other would be swamped by RF and even with frequency hopping, it wouldn’t cope.
You can do repeaters with two radios on DMR and while you can’t do it without opening the radios and using a discriminator feed, it works. I can’t see how a frequency hopping radio can work back to back.