Nope, unfortunately that is gullible thinking.It depends on what the investor want. If they are OK to hold the lease for a longer time and get the money from the Canal alone then no guaranties is an option. If there is a lack of investor interest in the project then the investors may want the return on investment in a shorter time in which case you need to take part of the risk and guaranties some revenue. At the end the profit will be commensurate with the risk they are taking.
Back in the 80'ties, 90'ties Turgut Ozal came up with a "brilliant" investment plan (not so brilliant afterwards)
His idea was "yap islet devret", in this way he was hoping that investors would build invest in dams in South east Turkey, operate them for 20-25 years and hand over the dam to Turkey.
He was selling it as getting dams for "free". Sounds nice for the gullible, but it was not that way. Dams have the nasty habit of usefulness, in time sediment brought by stream / rain etc. etc. starts to fill that dam, until the dam is slipped full of sediment and becomes useless (this happens in about 25 years). To prevent this and to get rid of this sediment dams need to be build with a flush through (which is the expensive form of dam building), so all those investors started to build the cheaper form of dams without flush through.
So these companies came invested in dams got the government incentives etc. made their profit with electricity production and handed over the dead dams (unable to produce any energy anymore) to the state (ölü esegin posasi)
With the canal project we are heading towards a new dam issue, there is no well founded planning, no profit calculation, no useful life calculations for the canal. But we see all type of assumptions, will bring a lot of investments, will bring a lot of profit, captains will chose to pay instead of free passage.
Sorry but I want to see well cared, engineered plans that shows the usefulness of that canal, it is totally absent. And when empty promises sound to good to be true, it usually is!