OK. Here you go
1. There are a number of telecaster pickup combinations which are made by fender as STOCK telecasters. There are ones with TWO HUMBUCKERS, stock. There are ones made with a THREE PICKUP ARRANGEMENT, STOCK. They all sound different.
2. Adding higher output pickups to an instrument is a common practice. It is so common, in fact, that Fender themselves make after market pickups which are hotter, quieter, etc. e.g. vintage noisless
3. The way a telecaster is built, you have to remove the entire bridge to change the bridge pickup. Due to the fact that the fretboard sticks out about 1/8-1/4 inch over the pickguard, you have to loosen the neck in order to take off the pickguard. Which you have to to in order to access the neck pickup.
(rude statement has been deleted... soo sorry)
Mickguard's suggestion regarding shaving away that portion of the pickguard which goes under the fretboard was a bit of good advice. If I decide that the new pickups aren't the sound I really want, I won't have to take the neck off to do any further work. Get It?
The neck not seating in the cavity properly is not due to it sitting on the pickguard, as it is only the fretboard which extends over it. The problem came about because of the removal and subsequent reattachment of the neck. Which, incidentally, I corrected, again using Mickguard's advice as regards a couple of clamps to hold the neck firmly in place while I reattached the screws holding the neck to the body.
4. As regards what a telecaster ought to sound like, What about Albert Collins? HMM? His has the aforementioned two-humbucker configuration and does not sound anything at all like merle haggard. Furthermore, just FYI, A great deal of the guitar work on the Led Zeppelin albums was done on telecasters. Jimmy Page definitely doesn't sound like Merle Haggard, or the Stones, or anybody else for that matter.
peace