Quoted from mbeardsley:"to the extent these items do not involve third party intellectual property rights requiring additional licensing"
Exactly as I was saying...they still need to secure the rights to other properties owned by other parties. To make a game like Elivra or TAF, PPS needs BOTH the Williams rights to the machine design (which they have), and the rights to those other properties (which they don't - yet).
Some of those rights may be easy to obtain, others may be very expensive (Indiana Jones, STTNG), others may be very complicated (TZ - due to Rod Serling's likeness being a separate thing from the TV series), and others may not be available at all (Elvira - depending upon the details of Stern's current license).
The MBr remake was reported to have been delayed because there was some hold up in finalizing the deal with Universal for their Monsters.
This is why it will be easier/cheaper to remake stuff like Whitewater, TOM, or TOTAN, since they already have all the rights they need for those machines.
How do you truly remake Whitewater when the topper doesn't appear to be something that can be replicated? Whitewaters without working toppers sell for considerably less for a reason.
Even if they make a different topper to go with it, is Whitewater really a game at a price point where it would be worth while to do a remake?