Sorry for my ignorance here, would the picatinny rail go over the extraction port (not sure of the proper term)?
The issue with the long action is that the rings Won't reach to where they will fit on the scope because of the distance.
A pic rail will not get in the way of loading your rifle. Also, being an ADL it can easily be converted to a BDL which has a hinged floor plate to unload the magazine. All you need is a BDL stock and a BDL magazine setup, which can be purchased from Brownells for around $150.
Personally, I don't like ADL's, I prefer the hinged floorplate of the BDL, so I have converted several. It's just a matter of loosening and tightening few bolts, a couple new parts, and a few minutes of your time.
This stock looks like a standard old Remington 700 plastic stock, but it is made of MUCH better materials, and it has a full aluminum bed block in it (factory stock does not) for accuracy and consistency.
Stock:
REMINGTON 700 SHORT ACTION BDL MEDALIST STOCK | Brownells
BDL Conversion:
700 LONG ACTION ADL-TO-BDL KITS | Brownells
As for the picatinny rail, I use them on ALL of my rifles, except one, and that is because I just haven't bought one to convert it yet. I use EGW HD bases, and Seekins Precision and TPS TSR rings (both brands of rings are high-quality, but I prefer the Seekins).
EGW HD Picatinny Rail 1 Piece Scope Mount | SWFA
TPS Tactical Scope 30mm Rings | SWFA
If you want something other than pic rail... I HIGHLY recommend the DNZ Game Reaper 1-piece rings/base. That's why I have one my 1 rifle that doesn't have a rail on it. It is one solid mount. I trust it enough to keep my $1,500 Kahles scope secure.
http://swfa.com/DNZ-Game-Reaper-30mm-Scopemount-P56385.aspx