totally honest answer:-
you will NEVER eliminate ladders,
WFP does NOT work on every job,
sometimes its that much hassle draggin hoses etc that its far quicker and easier to do trad,
i have both and NEED both,
when the windows are suitable wfp is BRILLIANT,
you WILL have jobs that require both trad and wfp,
going wfp without a van IS more hassle than its worth,
there are days when i HATE wfp,(especially in winter, you sometimes create a skating rink for your customers, and your equipment freezes up in van at night unless you bring it in- more hassle)
i know a guy who got wfp, he boasted so much about it (he spent 9 grand including van) that he talked his friend into getting it.most of his friends work wasnt suitable for wfp so he lost loads of his work and ended up selling it for a huge loss!
take HONEST advise, if its not broke dont mend it is sometimes a good frase.