To start with I would recommend balancing the power a bit probably use an inexpensive 250 watt front hub drive,with a TD2Z 350-500 36 VOLT MIDDRIVE,be reasonable and save some money , now you do not want this thing to be super fast because of stability concerns, actually you shouldnt need a dual controller just get a battery splitter, with both motors going this thing will eat hills, the Tongsheng middrive has built torque sensor( simplify) the hub motor can use throttle and or PAS. The TDZ middrives are reasonable price with up to 80 nm torque and you can dig around and find a used 26" 250 front wheel for under $50 and use a 'brick battery to save money, yada,yada, the sensors will give a good amount of control and so on.
I am planning on building a 750 -36 volt reverse trike for stability, keep us posted please, if you have the donor trike already it should be easy to make this thing under a $1000.
For anyone interested "Signal" a Chinese company makes the conversion kits for a leaning reverse trike for around $300.