That said, if you want to run a "high adventure" version, just reducing the drain value on various spells can accomplish it fairly quickly. Drain is your "mana pool" for that system, so tweaking it downwards a little bit means giving everyone more spells per encounter.
Personally, I have no problem with homebrew rules. I use them in abundance, especially when the actual rules are clunky or counter to the theme of the game I'm trying to run. One thing I find helpful is to gather up some people who are good with game systems. The college I just graduated form has a Game Design department, and a Game Design club. These are people who have all done in-depth study into how rules work, how they affect the gameplay experience.
Some advice we use when making changes to rules:
Have a Clear Goal: When you start to make a change to the rules, you should know why you are doing it. You should have a very specific objective in mind, and make sure your solution addresses that problem while affecting the rest of the game as little as necessary. Changes that are too broad or unfocused quickly spiral out of control. Even if your change is a big one, clearly defining what you intend to do and why you intend to do it can be the difference between a wonderful mod and a gigantic rules clusterf***. While you're changing healing magic, make sure you know the desired outcome. Are you more concerned with the difficulty of healing, or the damage it did to the caster? Because those are different problems. Do you want to put a condition on this better healing ability? Perhaps allowing the person to add their First Aid or Medicine dice to the casting would solve the problem without changing anything about the magic?
Start Simple, then Refine: Don't worry about the little details at first. If you're going to overhaul the healing system, start with a simple, easily explained change that will affect the change you want. For example, if you decide that the damage to a healing character for casting is too high, try cutting the healing Drain rating in half. From there, refine it through playtesting and thought experiments to see if there are specific changes needed, or other small things that need to be tweaked as a result, etc.
Study the Game from the Designer's Standpoint: Assuming we're talking about a fully-developed game, everything in it was included for a reason. It might be a crappy reason, or it might be irrelevant to your game or intent, but someone thought it needed to be there. Studying games from an objective "why did they do this?" standpoint is critical. When you change a rule, you're messing with the internal structure of the system, and you need to be aware of where that rule does (or doesn't) interact with other rules. Maybe healing was intentionally gimped because of the range of other options, such as drugs or cyberware, that help handle the problem. Changing that could make certain players brokenly powerful, or take away the advantage of other, very expensive abilities.
Playtest, Playtest, Playtest Try your homebrew rules in a one-shot or other low-risk setting. Involve a variety of people with different levels of play experience and familiarity with the system if possible. Solicit your players' opinions about the rules changes, and be open to tweaking or overhauling them if something doesn't end up working out. If you must use them in a game, always allow your players the option of changing their characters in response, and get their feedback about the changes. Even though dropping the Drain rating helps one character, maybe there's another who spent a TON of points into their endurance specifically to soak that damage. They have now gimped their character in other areas to counter a problem that no longer exists! They should have the chance to rectify this.
Me and a couple GM buddies have had great success with homebrew rules by sticking to these basic tennants. We've done a very successful point-buy version of DnD (yes, it was a pain in the ASS, but the result was cool.). We just finished a full rewrite of FATE 3.0 that we're calling AURA and getting ready to publish in a new setting, and dozens of smaller mods that have only occasionally caused trouble.
tl;dr: Game design is complicated, but homebrew can be done well with the right planning and study.
