Yeah, I have so many houserules and rule clarifications I could damn near write my own sourcebook. If you think my magic changes are in depth, you should see what I did to Technomancers.
On the issue of Alchemy, my problem with the core rules for it are that it is inherently worse than spellcasting in every way. Looking at the way Alchemy was designed makes me think that the developers were afraid to let it be good, expecting abuse, and at every step of the process they kept adding drawbacks until in the end, it's barely worth the effort.
Soaking drain in advance is a mixed bag, and not as good as it sounds. For one thing, it's only an advantage if you have time to take a nap before the run, which is rarely the case. Even if you do have time for a nap, you need to be able to recover all of your stun damage in as few rolls as possible, since you're most likely going to get a Potency of between 1 and 3, which means 2 to 6 hours before your preparations start to decay and you wasted your time.
Secondly, having to prepare everything in advance is as much of a disadvantage as it is an advantage, since you have to try to predict what spells you'll need, and how many times you'll need to cast it. For all the times I've GMed an Alchemist, I've found it incredibly common that they will make a bunch of preparations that they don't end up using, so they take drain for nothing.
I've playtested my houserule quite a bit and I'm pretty happy with the result, and it brings up Alchemy to be more in balance with the power of Sorcery.
As for my character, if the group is hurting for a combat monster then it sounds like I should go with the Troll. Extra muscle sent in, or maybe somebody Hopeless calls recommending it, both sound like good options to me.