As with anything WT / JW, a tithe would be given a unique title and implemented in a slightly different way from other religions.
As mentioned, WT has already implemented a version of a tithe, but the obligation is not placed on individual members, but on the congregation as a whole.
Individual congregation members/families were asked to indicate and commit to an amount they will provide on a monthly basis. Although not a percentage of income, those amounts were totalled and indicated to WT as that congregation's ongoing monthly 'contribution' to WT.
If an individual or family does not fulfil the commitment they indicated, other congregation members are then fully expected make-up for the shortfall.