Answers to your problems:

1) Lava power:
Lava power is unquestionably the best solution to get started on power.
~~
Stopping your players from acquiring this power will only resolve to 
create friction, and overall have players dislike the server enough
to not want to play on it. 
Solutions:
a) Make a Lava age(mystcraft), obtain the world border plugin, and then
	chunkload it. Players can then claim their section, and pump from there.
	This requires some upkeep on the staffs part, but that is the staffs 
	job after all. To make things go smoothly with any task given. 
	For even more consistent use of it, save a copy of the age, then
	re upload it every week or so to reset the lava age(and thus the lava).
	Can also world edit the lava back in as well as an alternative. 
b) Create a facility in which lava is sent to multiple tanks from an
	indefinite source, and at the cost of a fee, or donation(if super 
	money hungry) they can get access to one of the tanks. This facility
	would be spot loaded of course(have it all in 1 chunk).
	
2) Loaders:
From what I've come to understand, loaders are a big 'no-no' on this server.
This poses many problems to players. The main issue is for storage purposes,
as well as energy.
~~
Solution: 
Start by forming a new group. This group will be that of regulars/trusted players.
These players can apply for a spot loader to be placed by a staff. It will then be
logged down on a list, and checked every so often to ensure they are following the
regulations of it. 
From what I've learnt, 1 spot loader is just about enough to cover all storage and 
energy needs.


3)Regulars/Trusted
As suggested in topic two, create a new group of trusted/regulars. These are the people
who are to be generally more trusted than the mass of others. The best option I can think
of is that you have your regulars, which are just people who get a couple of special
perks just be being a regular(like multiple homes and such). When I was running the server
the permission list for Members is as follows:
		  Member:
			permissions:
			  essentials.chat.color: true
			  essentials.sleepingignored: true
			  essentials.msg.url: true
			  essentials.chat.url: true
			  essentials.recipe: true
			  essentials.workbench: true
			  essentials.warp: true
			  essentials.warp.list: true
			  essentials.sethome.multiple: true
			  essentials.getpos: true
			inheritance:
			- Novice
This is basically what I'm talking about when I mean regular. Basically a member who just gets
special little bonus's for being them. Since the way you're running the server, you'd probably 
want to take "essentials.warp.list" out of course, but I feel you Understand the principle.
~~
Persons in the trusted group would receive access to items such as the gravi gun, and are able 
to use banned items that bypass protections, but do so in a minimal way. 
Trusted would also be able to place water out side of claims/above ground, after all they are trusted.
This one typically is only given out to people who have applied for trusted and are already a regular.
(apply through the forums of course) 

This gives people a community goal in the game as well as a goal to become trusted. Happier players,
happier server.

4) Spawners:
Spawners are extremely useful, and are very quintessential to Modded minecraft.
Solution:
Outright ban the placement of soul cages and vanilla spawners. Then make it so 
regulars must register on the forums to aquire one, and a staff can place it
for them. Generally to be used more with the trusted group. Up to you though.
This will make it so staff can check on the spawners if server lag is ever present 
and shut them down if need be. Spawners will under no circumstance be in a loaded area,
else privilege will immediately be taken away.



The solutions I have just displayed completely take away the give an inch, take a mile problem.
Since you have to work through staff in order to do any of these things, people can't abuse it.

This brings me onto another issue.

5) Staff
Staff are quintessential for a server to run smoothly. 
Although you can't trust everyone with OP for obvious reasons, once we get a constant 50 people on,
the current admin aren't going to cut it in order to properly manage. There's just no way to cater to
that many people all the time.
This is where I recomend a 5th group of staff(currently Owner, Head admin, Admin, and Mod);
A Smod. Short for Super Mod, their role will be to manage the mods. They will be the really 
trusted, have full access to banned items, give command, restricted world edit, access to claims
and such. 
They will have all the tools that a admin will need to properly address most problems, without all the
ability to do everything. Just the things that you can't trust mod with. InvSee.modify, social spy, vanish,
things like that.
Please note that this is only for the persons who are extremely trusted and generally know what they're doing.
You don't have to give this out until you feel some one deserves it, if ever.

Since an admin may not always be present to fix a problem as soon as possible that is above a mods paygrade,
a Smod can pick up the slack in most cases. 
Nobody likes waiting an hour or two to receive a solution to a problem, nor should they have to. Adding another 
tier will decreases the time in which a problem may take to solve.
This also keeps an admins hands untied and levies some work from them.






The first 4 topics I feel really should be implemented, as from my current point of view they seem like extremely 
necessary things to implement.

The 5th one would also be fairly key I would think as well. The name can very to what ever you chose. Maybe 
Executive moderator(eMod?). Take a good look at all the Essential permissions(http://wiki.ess3.net/wiki/Command_Reference),
go through each one of them carefully and decide who needs what, what they can use and such. I'd even look at the world edit
as well. (assuming you do decide to add it. I even volunteer to make the group for you if you'd like)
		note: a way to limit the world edit for certain people is to go into the world edit config, and set the default block limit 
			2000-4000. Then in the permissions you give them(in this order) "worldedit.*: true" then "worldedit.limit: false". This 
			Makes it so they can only change the default amount of blocks at a time. This is not to prevent greifing, this is to
			prevent a possible slip up. (http://wiki.sk89q.com/wiki/WorldEdit/Permissions)