The MTH DCS system has a variable channel feature which will allow conventional control of trains with non command locomotives . There are two variable channels to run the two loops in the DCS system as it is supplied. To control your accessories and switches you will need to add the accessory interface AIU device. Since you have 7 switches, three operating tracks and several accessories you wish to control remotely, it sounds like you may need at least 2 AIU devices. You will also have a DCS signal on the track which will allow you to add a MTH command equipped locomotive which could be run in command mode .
You can do this with Lionel equipment as well. TMCC is no longer made, but you do see them for sale on the buy and sell board and the bay from time to time. Lionels system is Legacy and comes with a Command base and a handheld which gives you the ability to run TMCC or Legacy locomotives on your layout. To add conventional control, you need to add a device like a TPC 300 for each loop operating conventionally. There are also differrent switches that work with Legacy that you can use to operate your switches and accessories. If you upgrade to Gargraves or Ross Switches, you can buy them with Z stuff Z-2500 switch machines which can be dirrectly controlled by TMCC or Legacy I believe. The TPC devices will also run MTH command locos in conventional mode using the TMCC or Legacy Handheld.
You can also have command control of MTH locomotives by adding a DCS system. DCS and TMCC/Legacy will work on the same track simultaneously.
