Honestly, I feel for you. Except for fields we need in Workfront for tracking, finances, and such we've been very tempted to go back to our regimented Word forms on more than one occasion for input briefs. Our logic is, if we're not tracking the field data, does it need to live in Workfront's custom fields? We haven't flipped back yet, but I find myself recommending it when it comes up. :-( Also WF's custom forms print-our horribly and many folks prefer hardcopy to pass-around. If an Issue needs to convert to a Project OR to a Task, that means the same custom form in triplicate; a management headache. And then, as you pointed out: no draft mode. We've faked a draft mode but it's messy and caused alot of extra work and side-effects just to get it. What we did to mitigate was:
Our request/issue queue asks a series questions that narrow requestors down to tailored briefs (as well as what team the issue will be routed to). So no mega-brief with branching logic, just smaller ones for specific tasks. We manage about a dozen currently, which matched our Word briefs.
We use branching logic when we can on the forms to further cut-down on the apparent size of the brief; only show them relevant questions based on answers to other questions.
Kevin Quosig