The Legacy base will be fine. The Legacy engines or other modern engines for that matter probably will not be. Fast acting fuses could help prevent the modern electronics from getting fried if a derailment happens. The PW breaker will trip...eventually but probably not in time to protect the engines wiring or circuitry.
I would definitely add the inline fuses at minimal or get a modern transformer that has quick protection built in.
I also suspect that the drops may not help much. Depending on what you are running, with smoke units and lights you may be reaching the limit of the older transformer or maybe run the switches from another transformer.
