I'm just wrestling with how this would actually work, in practice. I'm not sure I'm following what you mean by 'boosting.'
As far as I know, PoTD resets everyone to lvl 1 when they start, and you have to work back up to 60 within the palace itself. Then you get a portion of the exp you earned within PoTD when you leave. The thing is, a carbon copy of that wouldn't work in PvP, because PvP'ing at lvl 1 would be just plain silly. Even if they started at lvl 20 or 30, there'd still be a problem with divided queues. The original Wolves Den had a similar issue back when there was a lvl 30 queue option. Eventually, the more dedicated PvP'ers get to cap, and the queue times for the more casual crowd at lower levels becomes astronomical. If we want to be as inclusive as possible, then this kind of system doesn't really work. It would seem fine on the first day, when everyone is reset and starting from scratch, but after a week or two there would be a huge divide in the player base and what level of matches they were getting into.
The alternative is just boosting everyone up to 60 within PvP content (which I think is what you're suggesting?), but I'm not sure that would work either ... Even with a tutorial, new players would have a ridiculous learning curve when setting up their hotbars and trying to figure out what all of their lvl 60 moves did. There are some things that only come with experience. Hotbars and specific move usage/utility are two of them. No amount of tutorials will solve that. The system would be much simpler and inclusive, but the actual player experience would be far more complicated and might intimidate new players, especially when a sizable amount of old-time PvP'ers already know what they're doing.
Increased lvl caps only compound that issue, because players who opt out of buying expansions will be left to awkwardly juggle a hotbar that has moves which they only have access to in PvP content. SE has FINALLY allowed us to store action points separately, but they have yet to allow PvP gear-sets to act independently from PvE gear sets, so there is no way to save a PvP hotbar separately from our PvE loudouts. Even if you have 'Pld' set up with two different gear sets (PvE and PvP) they share the same hotbars. Making changes to one, currently, changes the other as well. As things are, that's fine, because we only have PvP moves to worry about. However, if we allow non-expansion players to play at 60 in PvP they'll not only be adding PvP moves to their hotbars, but also all of the PvE additions from 50-60. That can seriously screw with their hotbars, as many of the lvl 60 moves are part of pre-existing combos or rotations. Without being able to save them separately, it would almost not be worth it to even try PvP, because they'd have to reorganize their hotbars depending on what kind of content they want to play that day.
I'm definitely not against the idea itself, I'm just not sure it would work smoothly. SE would have to make a lot of concessions and adjustments to implement it, and I'm sad to say that I just don't trust them to handle it without causing more people to be afraid of PvP, rather than open to trying it.