Sounds like your on the right track.
I purchased the Tippmann pro-lite in 96. I've never has a "gun down" day. Besides regular cleaning the only maintenance required has been the occasional O ring replacement.
About 3 years ago I felt the need for an upgrade. After weeks of contemplation and research I purchased an A-5 from 888paintball, at the time they had the best price. The Cyclone feeding system is what sets the A-5 apart from other markers. Someone may try to tell you they're electronic trigger can fire 30 times per second, but the truth is gravity cannot feed a paintball that frequently resulting in busted paintballs . The cyclone feed is essentially a revolving star inside a cylinder that is actuated by a gas powered piston. Everytime the marker is fired the star rotates 1/5 a turn placing a fresh paintball in the chamber. I have fired my A-5 8000+ times without breaking a single ball.
If you you play outdoors where long range is important the flatline is definatly the way to go. When we play out in the open its an unfair advantage. If you plan on playing speedball go with a traditional barrel.
I wouldn't worry about a scope. If you must I'd go with zero magnification like a red dot or holographic. Even with a flatline (which is capable of lobing 100 meters+) the distance is not great enough to require a zoom.
I have a remote tank, but I never use use it because it hampers my motion. I play ambidextrously, this allows me to show less of my body when emerging from behind a barrier. I prefer to use several 7oz tanks because they don't weigh enough to really slow me down/ impede movement (I'm always carrying a backup.)
Though it lacks the fit and finish, the A-5 is a formidable opponent to any $1000+ gun and in some key areas surpasses them.
I'll be more than glad to answer any questions