Substrate for Burrowers?

I'm in the process of designing a 75g tank and I am trying to decide on a substrate. My current tanks both have eco-complete in them and so far i've been quite happy with it, but it is quite expensive for a 75g tank. I was considering doing MTS with a blasting sand cap, but I am planning on having kuhli loaches which I hear like to burrow. Would that pose a problem for the loaches/my tank? I don't want them to have some sort of problem if they burrow down into the soil.

Also I had a bunch of other questions as well, i'll just rattle them off here:

1. How long does MTS last? Will I be able to grow plants for a year? 5 years? 10 years?

2. Do I still need to dose fertilizers if I do use MTS or can I do just the soil and CO2?

3. If MTS isn't suitable for burrowing loaches, can I do a 50/50 blasting sand eco-complete mix and then capped with blasting sand? I like the look/cost of the blasting sand better, but I would like to maintain the high CEC of eco-complete at least somewhat.

4. Is Eco-complete suitable for burrowers? It has a rather large grain size and is pretty rough, so is it usable at all or do I need to stick with just sandy materials?

Thanks in advance for any insight you can provide.